Zinc: A Necessary Ion for Mammalian Sperm Fertilization Competency

Karl Kerns, Michal Zigo, Peter Sutovsky, Karl Kerns, Michal Zigo, Peter Sutovsky

Abstract

The importance of zinc for male fertility only emerged recently, being propelled in part by consumer interest in nutritional supplements containing ionic trace minerals. Here, we review the properties, biological roles and cellular mechanisms that are relevant to zinc function in the male reproductive system, survey available peer-reviewed data on nutritional zinc supplementation for fertility improvement in livestock animals and infertility therapy in men, and discuss the recently discovered signaling pathways involving zinc in sperm maturation and fertilization. Emphasis is on the zinc-interacting sperm proteome and its involvement in the regulation of sperm structure and function, from spermatogenesis and epididymal sperm maturation to sperm interactions with the female reproductive tract, capacitation, fertilization, and embryo development. Merits of dietary zinc supplementation and zinc inclusion into semen processing media are considered with livestock artificial insemination (AI) and human assisted reproductive therapy (ART) in mind. Collectively, the currently available data underline the importance of zinc ions for male fertility, which could be harnessed to improve human reproductive health and reproductive efficiency in agriculturally important livestock species. Further research will advance the field of sperm and fertilization biology, provide new research tools, and ultimately optimize semen processing procedures for human infertility therapy and livestock AI.

Keywords: capacitation; fertility; fertilization; proteasome; sperm; zinc.

Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in this review; in the collection, analyses, or interpretation; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Summary of Zinc (Zn) signatures and free zinc ion (Zn2+) regulation of the fertilization competency of mammalian spermatozoa. (a) Super-resolution images of the non-capacitated boar sperm Zn signature 1 (a’) and acrosome-remodeled sperm Zn signature 3 (a'') acquired by the Leica TCP SP8 stimulated emission depletion (STED) microscope (free zinc ions in green, outer acrosomal membrane in cyan, remodeled sperm head plasma membrane in red; scale bars in gray: 5 μm). (a''') High Zn2+ concentration (2 mM) negatively regulates proton channel Hv1, responsible for the rise of intracellular pH, facilitating: (1) Ca2+ entry via CatSper and (2) protein tyrosine phosphorylation (pY), triggered by activation of soluble sperm adenylyl cyclase (SACY), increasing intracellular cAMP, activating protein kinase A (PKA) and phosphorylating protein tyrosine phosphatases (PTP) to an inactive state. For general capacitation pathway, review see Kerns et al., [144]). Following acrosome remodeling and exocytosis, zona pellucida (ZP) proteinases (acrosin, MMP2, and the 26S proteasome) implicated in endowing the spermatozoon with the ability to penetrate the ZP are activated. Zn2+, abundantly present in the fertilizing sperm triggered oocyte zinc shield, negatively regulates proteinase activities of spermatozoa bound to the zona or present in the perivitelline space, de-capacitating spermatozoa and serving as a newly proposed anti-polyspermy defense mechanism. (b) Capacitation-indicating state of the zinc signatures. Signature 1 spermatozoa are in a non-capacitated state. Signature 2 spermatozoa display hyperactivated motility. Only capacitating spermatozoa susceptible to progesterone (P4) chemoattraction exhibit chemorepulsion by Zn2+. Signature 3 spermatozoa exhibit acrosome remodeling while acrosomal exocytosis reportedly occurs in signature 4.

References

    1. Levaot N., Hershfinkel M. How cellular Zn2+ signaling drives physiological functions. Cell Calcium. 2018;75:53–63. doi: 10.1016/j.ceca.2018.08.004.
    1. Lee S.R. Critical Role of Zinc as Either an Antioxidant or a Prooxidant in Cellular Systems. Oxid. Med. Cell. Longev. 2018;2018:9156285. doi: 10.1155/2018/9156285.
    1. Lovell M.A. A potential role for alterations of zinc and zinc transport proteins in the progression of Alzheimer’s disease. J. Alzheimer’s Dis. 2009;16:471–483. doi: 10.3233/JAD-2009-0992.
    1. Szewczyk B. Zinc homeostasis and neurodegenerative disorders. Front. Aging Neurosc. 2013;5:33. doi: 10.3389/fnagi.2013.00033.
    1. Prakash A., Bharti K., Majeed A.B. Zinc: Indications in brain disorders. Fundament. Clin. Pharmacol. 2015;29:131–149. doi: 10.1111/fcp.12110.
    1. Prasad A.S. Zinc: Role in immunity, oxidative stress and chronic inflammation. Curr. Opin. Clin. Nutr. Metab. Care. 2009;12:646–652. doi: 10.1097/MCO.0b013e3283312956.
    1. Giachi G., Pallecchi P., Romualdi A., Ribechini E., Lucejko J.J., Colombini M.P., Mariotti Lippi M. Ingredients of a 2,000-y-old medicine revealed by chemical, mineralogical, and botanical investigations. Proc. Natl. Acad. Sci. USA. 2013;110:1193–1196. doi: 10.1073/pnas.1216776110.
    1. Prasad A.S. Discovery of human zinc deficiency: Its impact on human health and disease. Adv. Nutr. 2013;4:176–190. doi: 10.3945/an.112.003210.
    1. Outten C.E., O’Halloran T.V. Femtomolar sensitivity of metalloregulatory proteins controlling zinc homeostasis. Science. 2001;292:2488–2492. doi: 10.1126/science.1060331.
    1. Beyersmann D., Haase H. Functions of zinc in signaling, proliferation and differentiation of mammalian cells. Biometals. 2001;14:331–341. doi: 10.1023/A:1012905406548.
    1. Wastney M.E., Aamodt R.L., Rumble W.F., Henkin R.I. Kinetic analysis of zinc metabolism and its regulation in normal humans. Am. J. Physiol. 1986;251 Pt 2:R398–R408. doi: 10.1152/ajpregu.1986.251.2.R398.
    1. Bentley P.J., Grubb B.R. Effects of a zinc-deficient diet on tissue zinc concentrations in rabbits. J. Anim. Sci. 1991;69:4876–4882. doi: 10.2527/1991.69124876x.
    1. He L.S., Yan X.S., Wu D.C. Age-dependent variation of zinc-65 metabolism in LACA mice. Int. J. Radiat. Biol. 1991;60:907–916.
    1. Llobet J.M., Domingo J.L., Colomina M.T., Mayayo E., Corbella J. Subchronic oral toxicity of zinc in rats. Bull. Environ. Contam. Toxicol. 1988;41:36–43. doi: 10.1007/BF01689056.
    1. Jones M.M., Schoenheit J.E., Weaver A.D. Pretreatment and heavy metal LD50 values. Toxicol. Appl. Pharmacol. 1979;49:41–44. doi: 10.1016/0041-008X(79)90274-6.
    1. Prasad A.S., Oberleas D. Binding of zinc to amino acids and serum proteins in vitro. J. Lab. Clin. Med. 1970;76:416–425.
    1. Scott B.J., Bradwell A.R. Identification of the serum binding proteins for iron, zinc, cadmium, nickel, and calcium. Clin. Chem. 1983;29:629–633.
    1. Rukgauer M., Klein J., Kruse-Jarres J.D. Reference values for the trace elements copper, manganese, selenium, and zinc in the serum/plasma of children, adolescents, and adults. J. Trace Elem. Med. Biol. 1997;11:92–98. doi: 10.1016/S0946-672X(97)80032-6.
    1. Vallee B.L., Falchuk K.H. The biochemical basis of zinc physiology. Physiol. Rev. 1993;73:79–118. doi: 10.1152/physrev.1993.73.1.79.
    1. Lichten L.A., Cousins R.J. Mammalian zinc transporters: Nutritional and physiologic regulation. Ann. Rev. Nutr. 2009;29:153–176. doi: 10.1146/annurev-nutr-033009-083312.
    1. Foresta C., Garolla A., Cosci I., Menegazzo M., Ferigo M., Gandin V., De Toni L. Role of zinc trafficking in male fertility: From germ to sperm. Hum. Reprod. 2014;29:1134–1145. doi: 10.1093/humrep/deu075.
    1. Croxford T.P., McCormick N.H., Kelleher S.L. Moderate zinc deficiency reduces testicular Zip6 and Zip10 abundance and impairs spermatogenesis in mice. J. Nutr. 2011;141:359–365. doi: 10.3945/jn.110.131318.
    1. Zalewski P.D., Forbes I.J., Betts W.H. Correlation of apoptosis with change in intracellular labile Zn(II) using zinquin [(2-methyl-8-p-toluenesulphonamido-6-quinolyloxy)acetic acid], a new specific fluorescent probe for Zn(II) Biochem. J. 1993;296 Pt 2:403–408. doi: 10.1042/bj2960403.
    1. Wellenreuther G., Cianci M., Tucoulou R., Meyer-Klaucke W., Haase H. The ligand environment of zinc stored in vesicles. Biochem. Biophys. Res. Commun. 2009;380:198–203. doi: 10.1016/j.bbrc.2009.01.074.
    1. Qin Y., Dittmer P.J., Park J.G., Jansen K.B., Palmer A.E. Measuring steady-state and dynamic endoplasmic reticulum and Golgi Zn2+ with genetically encoded sensors. Proc. Natl. Acad. Sci. USA. 2011;108:7351–7356. doi: 10.1073/pnas.1015686108.
    1. Sensi S.L., Canzoniero L.M., Yu S.P., Ying H.S., Koh J.Y., Kerchner G.A., Choi D.W. Measurement of intracellular free zinc in living cortical neurons: Routes of entry. J. Neurosci. 1997;17:9554–9564. doi: 10.1523/JNEUROSCI.17-24-09554.1997.
    1. Vinkenborg J.L., Nicolson T.J., Bellomo E.A., Koay M.S., Rutter G.A., Merkx M. Genetically encoded FRET sensors to monitor intracellular Zn2+ homeostasis. Nat. Methods. 2009;6:737–740. doi: 10.1038/nmeth.1368.
    1. Tapiero H., Tew K.D. Trace elements in human physiology and pathology: Zinc and metallothioneins. Biomed. Pharmacother. 2003;57:399–411. doi: 10.1016/S0753-3322(03)00081-7.
    1. Coyle P., Philcox J.C., Carey L.C., Rofe A.M. Metallothionein: The multipurpose protein. Cell. Mol. Life Sci. 2002;59:627–647. doi: 10.1007/s00018-002-8454-2.
    1. Blindauer C.A., Leszczyszyn O.I. Metallothioneins: Unparalleled diversity in structures and functions for metal ion homeostasis and more. Nat. Prod. Rep. 2010;27:720–741. doi: 10.1039/b906685n.
    1. Maret W., Krezel A. Cellular zinc and redox buffering capacity of metallothionein/thionein in health and disease. Mol. Med. 2007;13:371–375. doi: 10.2119/2007-00036.Maret.
    1. Zhao M.H., Kwon J.W., Liang S., Kim S.H., Li Y.H., Oh J.S., Kim N.H., Cui X.S. Zinc regulates meiotic resumption in porcine oocytes via a protein kinase C-related pathway. PLoS ONE. 2014;9:e102097. doi: 10.1371/journal.pone.0102097.
    1. Kim A.M., Bernhardt M.L., Kong B.Y., Ahn R.W., Vogt S., Woodruff T.K., O’Halloran T.V. Zinc sparks are triggered by fertilization and facilitate cell cycle resumption in mammalian eggs. ACS Chem. Biol. 2011;6:716–723. doi: 10.1021/cb200084y.
    1. Kim A.M., Vogt S., O’Halloran T.V., Woodruff T.K. Zinc availability regulates exit from meiosis in maturing mammalian oocytes. Nat. Chem. Biol. 2010;6:674–681. doi: 10.1038/nchembio.419.
    1. Que E.L., Duncan F.E., Bayer A.R., Philips S.J., Roth E.W., Bleher R., Gleber S.C., Vogt S., Woodruff T.K., O’Halloran T.V. Zinc sparks induce physiochemical changes in the egg zona pellucida that prevent polyspermy. Integr. Biol. 2017;9:135–144. doi: 10.1039/C6IB00212A.
    1. Yamaguchi S., Miura C., Kikuchi K., Celino F.T., Agusa T., Tanabe S., Miura T. Zinc is an essential trace element for spermatogenesis. Proc. Natl. Acad. Sci. USA. 2009;106:10859–10864. doi: 10.1073/pnas.0900602106.
    1. Elgazar V., Razanov V., Stoltenberg M., Hershfinkel M., Huleihel M., Nitzan Y.B., Lunenfeld E., Sekler I., Silverman W.F. Zinc-regulating proteins, ZnT-1, and metallothionein I/II are present in different cell populations in the mouse testis. J. Histochem. Cytochem. 2005;53:905–912. doi: 10.1369/jhc.4A6482.2005.
    1. Sugihara T., Wadhwa R., Kaul S.C., Mitsui Y. A novel testis-specific metallothionein-like protein, tesmin, is an early marker of male germ cell differentiation. Genomics. 1999;57:130–136. doi: 10.1006/geno.1999.5756.
    1. Chi Z.H., Feng W.Y., Gao H.L., Zheng W., Huang L., Wang Z.Y. ZNT7 and Zn2+ are present in different cell populations in the mouse testis. Histol. Histopathol. 2009;24:25–30.
    1. Shihan M., Chan K.H., Konrad L., Scheiner-Bobis G. Non-classical testosterone signaling in spermatogenic GC-2 cells is mediated through ZIP9 interacting with Gnalpha11. Cell. Signal. 2015;27:2077–2086. doi: 10.1016/j.cellsig.2015.07.013.
    1. Lopez-Gonzalez I., Trevino C.L., Darszon A. Regulation of Spermatogenic Cell T-Type Ca2+ Currents by Zn2+: Implications in Male Reproductive Physiology. J. Cell. Physiol. 2016;231:659–667. doi: 10.1002/jcp.25112.
    1. Barney G.H., Orgebin-Crist M.C., Macapinalac M.P. Genesis of esophageal parakeratosis and histologic changes in the testes of the zinc-deficient rat and their reversal by zinc repletion. J. Nutr. 1968;95:526–534. doi: 10.1093/jn/95.4.526.
    1. Baccetti B., Pallini V., Burrini A.G. The accessory fibers of the sperm tail. II. Their role in binding zinc in mammals and cephalopods. J. Ultrastruct. Res. 1976;54:261–275. doi: 10.1016/S0022-5320(76)80155-4.
    1. Bedford J.M., Calvin H.I. Changes in -S-S- linked structures of the sperm tail during epididymal maturation, with comparative observations in sub-mammalian species. J. Exp. Zool. 1974;187:181–204. doi: 10.1002/jez.1401870202.
    1. Bjorndahl L., Kjellberg S., Roomans G.M., Kvist U. The human sperm nucleus takes up zinc at ejaculation. Int. J. Androl. 1986;9:77–80. doi: 10.1111/j.1365-2605.1986.tb00869.x.
    1. Porath J., Carlsson J., Olsson I., Belfrage G. Metal chelate affinity chromatography, a new approach to protein fractionation. Nature. 1975;258:598–599. doi: 10.1038/258598a0.
    1. Bjorndahl L., Kvist U. Human sperm chromatin stabilization: A proposed model including zinc bridges. Mol. Hum. Reprod. 2010;16:23–29. doi: 10.1093/molehr/gap099.
    1. Bjorndahl L., Kvist U. A model for the importance of zinc in the dynamics of human sperm chromatin stabilization after ejaculation in relation to sperm DNA vulnerability. Syst. Biol. Reprod. Med. 2011;57:86–92. doi: 10.3109/19396368.2010.516306.
    1. Kvist U. Importance of spermatozoal zinc as temporary inhibitor of sperm nuclear chromatin decondensation ability in man. Acta Physiol. Scand. 1980;109:79–84. doi: 10.1111/j.1748-1716.1980.tb06567.x.
    1. Kvist U. Sperm nuclear chromatin decondensation ability. An in vitro study on ejaculated human spermatozoa. Acta physiol. Scand. Suppl. 1980;486:1–24.
    1. Roomans G.M., Lundevall E., Bjorndahl L., Kvist U. Removal of zinc from subcellular regions of human spermatozoa by EDTA treatment studied by X-ray microanalysis. Int. J. Androl. 1982;5:478–486. doi: 10.1111/j.1365-2605.1982.tb00279.x.
    1. Henkel R., Baldauf C., Bittner J., Weidner W., Miska W. Elimination of zinc from the flagella of spermatozoa during epididymal transit is important for motility. Reprod. Technol. 2001;10:6.
    1. Andrews J.C., Nolan J.P., Hammerstedt R.H., Bavister B.D. Role of zinc during hamster sperm capacitation. Biol. Reprod. 1994;51:1238–1247. doi: 10.1095/biolreprod51.6.1238.
    1. Steven F.S., Griffin M.M., Chantler E.N. Inhibition of human and bovine sperm acrosin by divalent metal ions. Possible role of zinc as a regulator of acrosin activity. Int. J. Androl. 1982;5:401–412. doi: 10.1111/j.1365-2605.1982.tb00270.x.
    1. Johnsen O., Eliasson R., Lofman C.O. Inhibition of the gelatinolytic and esterolytic activity of human sperm acrosin by zinc. Acta Physiol. Scand. 1982;114:475–476. doi: 10.1111/j.1748-1716.1982.tb07013.x.
    1. Bettger W.J., O’Dell B.L. A critical physiological role of zinc in the structure and function of biomembranes. Life Sci. 1981;28:1425–1438. doi: 10.1016/0024-3205(81)90374-X.
    1. Mankad M., Sathawara N.G., Doshi H., Saiyed H.N., Kumar S. Seminal plasma zinc concentration and alpha-glucosidase activity with respect to semen quality. Biol. Trace Elem. Res. 2006;110:97–106. doi: 10.1385/BTER:110:2:97.
    1. Riffo M., Leiva S., Astudillo J. Effect of zinc on human sperm motility and the acrosome reaction. Int. J. Androl. 1992;15:229–237. doi: 10.1111/j.1365-2605.1992.tb01343.x.
    1. Acott T.S., Carr D.W. Inhibition of bovine spermatozoa by caudal epididymal fluid: II. Interaction of pH and a quiescence factor. Biol. Reprod. 1984;30:926–935. doi: 10.1095/biolreprod30.4.926.
    1. Ho H.C., Granish K.A., Suarez S.S. Hyperactivated motility of bull sperm is triggered at the axoneme by Ca2+ and not cAMP. Dev. Biol. 2002;250:208–217. doi: 10.1006/dbio.2002.0797.
    1. Babcock D.F., Rufo G.A., Jr., Lardy H.A. Potassium-dependent increases in cytosolic pH stimulate metabolism and motility of mammalian sperm. Proc. Natl. Acad. Sci. USA. 1983;80:1327–1331. doi: 10.1073/pnas.80.5.1327.
    1. Bray T.M., Bettger W.J. The physiological role of zinc as an antioxidant. Free Radic. Biol. Med. 1990;8:281–291. doi: 10.1016/0891-5849(90)90076-U.
    1. Narasimhaiah M., Arunachalam A., Sellappan S., Mayasula V.K., Guvvala P.R., Ghosh S.K., Chandra V., Ghosh J., Kumar H. Organic zinc and copper supplementation on antioxidant protective mechanism and their correlation with sperm functional characteristics in goats. Reprod. Domest. Anim. 2018;53:644–654. doi: 10.1111/rda.13154.
    1. Arver S. Zinc and zinc ligands in human seminal plasma. I. Methodological aspects and normal findings. Int. J. Androl. 1980;3:629–642. doi: 10.1111/j.1365-2605.1980.tb00151.x.
    1. Arver S., Eliasson R. Zinc and zinc ligands in human seminal plasma. II. Contribution by ligands of different origin to the zinc binding properties of human seminal plasma. Acta Physiol. Scand. 1982;115:217–224. doi: 10.1111/j.1748-1716.1982.tb07068.x.
    1. Arver S. Zinc and zinc ligands in human seminal plasma. III. The principal low molecular weight zinc ligand in prostatic secretion and seminal plasma. Acta Physiol. Scand. 1982;116:67–73. doi: 10.1111/j.1748-1716.1982.tb10600.x.
    1. Siciliano L., De Stefano C., Petroni M.F., Vivacqua A., Rago V., Carpino A. Prostatic origin of a zinc binding high molecular weight protein complex in human seminal plasma. Mol. Hum. Reprod. 2000;6:215–218. doi: 10.1093/molehr/6.3.215.
    1. Robert M., Gagnon C. Semenogelin I: A coagulum forming, multifunctional seminal vesicle protein. Cell. Mol. Life Sci. 1999;55:944–960. doi: 10.1007/s000180050346.
    1. Vivacqua A., Siciliano L., Sabato M., Palma A., Carpino A. Prostasomes as zinc ligands in human seminal plasma. Int. J. Androl. 2004;27:27–31. doi: 10.1111/j.1365-2605.2004.00441.x.
    1. Mogielnicka-Brzozowska M., Wysocki P., Strzezek J., Kordan W. Zinc-binding proteins from boar seminal plasma—Isolation, biochemical characteristics and influence on spermatozoa stored at 4 degrees C. Acta Biochim. Pol. 2011;58:171–177.
    1. Johnson L., Wikström S., Nylander G. The Vehicle for Zinc in the Prostatic Secretion of Dogs. Scand. J. Urol. Nephrol. 1969;3:9–11. doi: 10.3109/00365596909135373.
    1. Mogielnicka-Brzozowska M., Strzezek R., Wasilewska K., Kordan W. Prostasomes of canine seminal plasma—Zinc-binding ability and effects on motility characteristics and plasma membrane integrity of spermatozoa. Reprod. Domest. Anim. 2015;50:484–491. doi: 10.1111/rda.12516.
    1. Andreini C., Banci L., Bertini I., Rosato A. Counting the zinc-proteins encoded in the human genome. J. Proteome Res. 2006;5:196–201. doi: 10.1021/pr050361j.
    1. Coleman J.E. Zinc proteins: Enzymes, storage proteins, transcription factors, and replication proteins. Ann. Rev. Biochem. 1992;61:897–946. doi: 10.1146/annurev.bi.61.070192.004341.
    1. Vallee B.L., Coleman J.E., Auld D.S. Zinc fingers, zinc clusters, and zinc twists in DNA-binding protein domains. Proc. Natl. Acad. Sci. USA. 1991;88:999–1003. doi: 10.1073/pnas.88.3.999.
    1. Bianchi F., Rousseaux-Prevost R., Sautiere P., Rousseaux J. P2 protamines from human sperm are zinc -finger proteins with one CYS2/HIS2 motif. Biochem. Biophys. Res. Commun. 1992;182:540–547. doi: 10.1016/0006-291X(92)91766-J.
    1. Seiler H.G., Sigel H. Handbook on Toxicity of Inorganic Compounds. Marcel Dekker; New York, NY, USA: 1988.
    1. Vallee B.L., Auld D.S. Zinc coordination, function, and structure of zinc enzymes and other proteins. Biochemistry. 1990;29:5647–5659. doi: 10.1021/bi00476a001.
    1. Vallee B.L., Auld D.S. Active zinc binding sites of zinc metalloenzymes. In: Birkedal-Hansen H., Werb Z., Welgus H., Van Wart H., editors. Matrix Metalloproteinases and Inhibitors. Fischer; Stuttgart, Germany: 1992. p. 5.
    1. Cui N., Hu M., Khalil R.A. Biochemical and Biological Attributes of Matrix Metalloproteinases. Prog. Mol. Biol. Transl. Sci. 2017;147:1–73.
    1. Nagase H., Visse R., Murphy G. Structure and function of matrix metalloproteinases and TIMPs. Cardiovasc. Res. 2006;69:562–573. doi: 10.1016/j.cardiores.2005.12.002.
    1. Shimokawa Ki K., Katayama M., Matsuda Y., Takahashi H., Hara I., Sato H., Kaneko S. Matrix metalloproteinase (MMP)-2 and MMP-9 activities in human seminal plasma. Mol. Hum. Reprod. 2002;8:32–36. doi: 10.1093/molehr/8.1.32.
    1. Tentes I., Asimakopoulos B., Mourvati E., Diedrich K., Al-Hasani S., Nikolettos N. Matrix metalloproteinase (MMP)-2 and MMP-9 in seminal plasma. J. Assist. Reprod. Genet. 2007;24:278–281. doi: 10.1007/s10815-007-9129-6.
    1. Saengsoi W., Shia W.Y., Shyu C.L., Wu J.T., Warinrak C., Lee W.M., Cheng F.P. Detection of matrix metalloproteinase (MMP)-2 and MMP-9 in canine seminal plasma. Anim. Reprod. Sci. 2011;127:114–119. doi: 10.1016/j.anireprosci.2011.07.004.
    1. Warinrak C., Wu J.T., Hsu W.L., Liao J.W., Chang S.C., Cheng F.P. Expression of matrix metalloproteinases (MMP-2, MMP-9) and their inhibitors (TIMP-1, TIMP-2) in canine testis, epididymis and semen. Reprod. Domest. Anim. 2015;50:48–57. doi: 10.1111/rda.12448.
    1. Buchman-Shaked O., Kraiem Z., Gonen Y., Goldman S. Presence of matrix metalloproteinases and tissue inhibitor of matrix metalloproteinase in human sperm. J. Androl. 2002;23:702–708.
    1. Ferrer M., Rodriguez H., Zara L., Yu Y., Xu W., Oko R. MMP2 and acrosin are major proteinases associated with the inner acrosomal membrane and may cooperate in sperm penetration of the zona pellucida during fertilization. Cell. Tissue Res. 2012;349:881–895. doi: 10.1007/s00441-012-1429-1.
    1. Kratz E.M., Kaluza A., Ferens-Sieczkowska M., Olejnik B., Fiutek R., Zimmer M., Piwowar A. Gelatinases and their tissue inhibitors are associated with oxidative stress: A potential set of markers connected with male infertility. Reprod. Fertil. Dev. 2016;28:1029–1037. doi: 10.1071/RD14268.
    1. Atabakhsh M., Khodadadi I., Amiri I., Mahjub H., Tavilani H. Activity of Matrix Metalloproteinase 2 and 9 in Follicular Fluid and Seminal Plasma and Its Relation to Embryo Quality and Fertilization Rate. J. Reprod. Infertil. 2018;19:140–145.
    1. McCord J.M., Fridovich I. Superoxide dismutase. An enzymic function for erythrocuprein (hemocuprein) J. Biol. Chem. 1969;244:6049–6055.
    1. Marklund S.L. Extracellular superoxide dismutase and other superoxide dismutase isoenzymes in tissues from nine mammalian species. Biochem. J. 1984;222:649–655. doi: 10.1042/bj2220649.
    1. Alvarez J.G., Touchstone J.C., Blasco L., Storey B.T. Spontaneous lipid peroxidation and production of hydrogen peroxide and superoxide in human spermatozoa. Superoxide dismutase as major enzyme protectant against oxygen toxicity. J. Androl. 1987;8:338–348. doi: 10.1002/j.1939-4640.1987.tb00973.x.
    1. Beconi M.T., Francia C.R., Mora N.G., Affranchino M.A. Effect of natural antioxidants on frozen bovine semen preservation. Theriogenology. 1993;40:841–851. doi: 10.1016/0093-691X(93)90219-U.
    1. O’Flaherty C., Beconi M., Beorlegui N. Effect of natural antioxidants, superoxide dismutase and hydrogen peroxide on capacitation of frozen-thawed bull spermatozoa. Andrologia. 1997;29:269–275. doi: 10.1111/j.1439-0272.1997.tb00481.x.
    1. Kowalowka M., Wysocki P., Fraser L., Strzezek J. Extracellular superoxide dismutase of boar seminal plasma. Reprod. Domest. Anim. 2008;43:490–496. doi: 10.1111/j.1439-0531.2007.00943.x.
    1. Strzezek R., Fraser L. Characteristics of spermatozoa of whole ejaculate and sperm-rich fraction of dog semen following exposure to media varying in osmolality. Reprod. Biol. 2009;9:113–126. doi: 10.1016/S1642-431X(12)60021-7.
    1. Marti E., Mara L., Marti J.I., Muino-Blanco T., Cebrian-Perez J.A. Seasonal variations in antioxidant enzyme activity in ram seminal plasma. Theriogenology. 2007;67:1446–1454. doi: 10.1016/j.theriogenology.2007.03.002.
    1. Peeker R., Abramsson L., Marklund S.L. Superoxide dismutase isoenzymes in human seminal plasma and spermatozoa. Mol. Hum. Reprod. 1997;3:1061–1066. doi: 10.1093/molehr/3.12.1061.
    1. Park K., Jeon S., Song Y.-J., Yi L.S.H. Proteomic analysis of boar spermatozoa and quantity changes of superoxide dismutase 1, glutathione peroxidase, and peroxiredoxin 5 during epididymal maturation. Anim. Reprod. Sci. 2012;135:53–61. doi: 10.1016/j.anireprosci.2012.08.027.
    1. Sikka S.C. Relative impact of oxidative stress on male reproductive function. Curr. Med. Chem. 2001;8:851–862. doi: 10.2174/0929867013373039.
    1. Dhanda O.P., Rao B.R., Razdan M.N. Sorbitol dehydrogenase & hyaluronidase activity in buffalo semen. Indian J. Exp. Biol. 1981;19:286.
    1. Gavella M., Cvitkovic P. Semen LDH-X deficiency and male infertility. Arch. Androl. 1985;15:173–176. doi: 10.3109/01485018508986907.
    1. Virji N. LDH-C4 in human seminal plasma and its relationship to testicular function. I. Methodological aspects. Int. J. Androl. 1985;8:193–200. doi: 10.1111/j.1365-2605.1985.tb00834.x.
    1. Wheat T.E., Goldberg E. Sperm-specific lactate dehydrogenase C4: Antigenic structure and immunosuppression of fertility. In: Scandalios J.G., Whitt G.S., editors. Isozymes. Current Topics in Biological and Medical Research. Liss; New York, NY, USA: 1983. pp. 113–130.
    1. Duan C., Goldberg E. Inhibition of lactate dehydrogenase C4 (LDH-C4) blocks capacitation of mouse sperm in vitro. Cytogenet. Genome Res. 2003;103:352–359. doi: 10.1159/000076824.
    1. Zimmerman S.W., Yi Y.J., Sutovsky M., van Leeuwen F.W., Conant G., Sutovsky P. Identification and characterization of RING-finger ubiquitin ligase UBR7 in mammalian spermatozoa. Cell. Tissue Res. 2014;356:261–278. doi: 10.1007/s00441-014-1808-x.
    1. Zimmerman S.W., Manandhar G., Yi Y.J., Gupta S.K., Sutovsky M., Odhiambo J.F., Powell M.D., Miller D.J., Sutovsky P. Sperm proteasomes degrade sperm receptor on the egg zona pellucida during mammalian fertilization. PLoS ONE. 2011;6:e17256. doi: 10.1371/journal.pone.0017256.
    1. Jaiswal A., Joshi P., Kumar M.V., Panda J.N., Singh L.N. Angiotensin converting enzyme in the testis and epididymis of mammals. Andrologia. 1984;16:410–416. doi: 10.1111/j.1439-0272.1984.tb00385.x.
    1. Yotsumoto H., Sato S., Shibuya M. Localization of angiotensin converting enzyme (dipeptidyl carboxypeptidase) in swine sperm by immunofluorescence. Life Sci. 1984;35:1257–1261. doi: 10.1016/0024-3205(84)90096-1.
    1. Krassnigg F., Niederhauser H., Placzek R., Frick J., Schill W.B. Investigations on the functional role of angiotensin converting enzyme (ACE) in human seminal plasma. Adv. Exp. Med. Biol. 1986;198 Pt A:477–485.
    1. Brentjens J.R., Matsuo S., Andres G.A., Caldwell P.R., Zamboni L. Gametes contain angiotensin converting enzyme (kininase II) Experientia. 1986;42:399–402. doi: 10.1007/BF02118626.
    1. Vivet F., Callard P., Gamoudi A. Immunolocalization of angiotensin 1 converting enzyme in the human male genital tract by the avidin-biotin-complex method. Histochemistry. 1987;86:499–502. doi: 10.1007/BF00500623.
    1. Dobrinski I., Ignotz G.G., Fagnan M.S., Yudin S.I., Ball B.A. Isolation and characterization of a protein with homology to angiotensin converting enzyme from the periacrosomal plasma membrane of equine spermatozoa. Mol. Reprod. Dev. 1997;48:251–260. doi: 10.1002/(SICI)1098-2795(199710)48:2<251::AID-MRD13>;2-0.
    1. Gatti J.L., Druart X., Guerin Y., Dacheux F., Dacheux J.L. A 105- to 94-kilodalton protein in the epididymal fluids of domestic mammals is angiotensin I-converting enzyme (ACE); evidence that sperm are the source of this ACE. Biol. Reprod. 1999;60:937–945. doi: 10.1095/biolreprod60.4.937.
    1. Reeves P.G., O’Dell B.L. Zinc deficiency in rats and angiotensin-converting enzyme activity: Comparative effects on lung and testis. J. Nutr. 1988;118:622–626. doi: 10.1093/jn/118.5.622.
    1. Singh U.S., Kumar M.V., Panda J.N. Angiotensin converting enzyme in semen and its possible role in capacitation. Andrologia. 1985;17:472–475. doi: 10.1111/j.1439-0272.1985.tb01044.x.
    1. Kondoh G., Tojo H., Nakatani Y., Komazawa N., Murata C., Yamagata K., Maeda Y., Kinoshita T., Okabe M., Taguchi R., et al. Angiotensin-converting enzyme is a GPI-anchored protein releasing factor crucial for fertilization. Nat. Med. 2005;11:160–166. doi: 10.1038/nm1179.
    1. Zigo M., Jonakova V., Sulc M., Manaskova-Postlerova P. Characterization of sperm surface protein patterns of ejaculated and capacitated boar sperm, with the detection of ZP binding candidates. Int. J. Biol. Macromol. 2013;61:322–328. doi: 10.1016/j.ijbiomac.2013.07.014.
    1. Einarsson S., Gustafsson B., Settergren I. Alkaline phosphatase activity of epididymal contents in boars with normal or reduced spermatogenesis. Andrologia. 1976;8:25–28. doi: 10.1111/j.1439-0272.1976.tb01640.x.
    1. Bell D.J., Lake P.E. A comparison of phosphomonesterase activities in the seminal plasmas of the domestic cock, turkey tom, boar, bull, buck rabbit and of man. J. Reprod. Fertil. 1962;3:363–368. doi: 10.1530/jrf.0.0030363.
    1. Soucek D.A., Vary J.C. Some properties of acid and alkaline phosphates from boar sperm plasma membranes. Biol. Reprod. 1984;31:687–693. doi: 10.1095/biolreprod31.4.687.
    1. Bucci D., Isani G., Giaretta E., Spinaci M., Tamanini C., Ferlizza E., Galeati G. Alkaline phosphatase in boar sperm function. Andrology. 2014;2:100–106. doi: 10.1111/j.2047-2927.2013.00159.x.
    1. Gillis B.A., Tamblyn T.M. Association of bovine sperm aldolase with sperm subcellular components. Biol. Reprod. 1984;31:25–35. doi: 10.1095/biolreprod31.1.25.
    1. Mildvan A.S., Kobes R.D., Rutter W.J. Magnetic resonance studies of the role of the divalent cation in the mechanism of yeast aldolase. Biochemistry. 1971;10:1191–1204. doi: 10.1021/bi00783a016.
    1. Dafeldecker W.P., Vallee B.L. Organ-specific human alcohol dehydrogenase: Isolation and characterization of isozymes from testis. Biochem. Biophys. Res. Commun. 1986;134:1056–1063. doi: 10.1016/0006-291X(86)90358-X.
    1. Khokha A.M., Voronov P.P., Zimatkin S.M. Immunoenzyme and immunohistochemical analysis of class III alcohol dehydrogenase from human testis. Biokhimiia. 1994;59:997–1002.
    1. Cho C. Testicular and epididymal ADAMs: Expression and function during fertilization. Nat. Rev. Urol. 2012;9:550–560. doi: 10.1038/nrurol.2012.167.
    1. Chunghee C. Mammalian ADAMs with Testis-Specific or -Predominant Expression. In: Hooper N., Lendeckel U., editors. The ADAM Family of Proteases. Springer; Dordrecht, The Netherlands: 2005. pp. 239–259.
    1. Loeb J. On Some Non-Specific Factors for the Entrance of the Spermatozoon into the Egg. Science. 1914;40:316–318. doi: 10.1126/science.40.1026.316.
    1. Rogers J., Yanagimachi R. Release of hyaluronidase from guinea-pig spermatozoa through an acrosome reaction initiated by calcium. J. Reprod. Fertil. 1975;44:135–138. doi: 10.1530/jrf.0.0440135.
    1. Yanagimachi R., Kanoh Y. Manner of Sperm Entry in Herring Egg, with Special Reference to the Role of Calcium Ions in Fertilization. J. Fac. Sci. Hokkaido Univ. 1953;11:487.
    1. Yanagimachi R., Usui N. Calcium dependence of the acrosome reaction and activation of guinea pig spermatozoa. Exp. Cell Res. 1974;89:161–174. doi: 10.1016/0014-4827(74)90199-2.
    1. Gervasi M.G., Visconti P.E. Chang’s meaning of capacitation: A molecular perspective. Mol. Reprod. Dev. 2016;83:860–874. doi: 10.1002/mrd.22663.
    1. Chang M.C. Fertilizing capacity of spermatozoa deposited into the fallopian tubes. Nature. 1951;168:697–698. doi: 10.1038/168697b0.
    1. Kerns K., Zigo M., Drobnis E.Z., Sutovsky M., Sutovsky P. Zinc ion flux during mammalian sperm capacitation. Nat. Commun. 2018;9:2061. doi: 10.1038/s41467-018-04523-y.
    1. De Jonge C. Biological basis for human capacitation-revisited. Hum. Reprod. Update. 2017;23:289–299. doi: 10.1093/humupd/dmw048.
    1. Florman H.M., Jungnickel M.K., Sutton K.A. Shedding light on sperm pHertility. Cell. 2010;140:310–312. doi: 10.1016/j.cell.2010.01.035.
    1. Zeng Y., Oberdorf J.A., Florman H.M. pH regulation in mouse sperm: Identification of Na(+)-, Cl(−)-, and HCO3(-)-dependent and arylaminobenzoate-dependent regulatory mechanisms and characterization of their roles in sperm capacitation. Dev. Biol. 1996;173:510–520. doi: 10.1006/dbio.1996.0044.
    1. Wang D., Hu J., Bobulescu I.A., Quill T.A., McLeroy P., Moe O.W., Garbers D.L. A sperm-specific Na+/H+ exchanger (sNHE) is critical for expression and in vivo bicarbonate regulation of the soluble adenylyl cyclase (sAC) Proc. Natl. Acad. Sci. USA. 2007;104:9325–9330. doi: 10.1073/pnas.0611296104.
    1. Lishko P.V., Botchkina I.L., Fedorenko A., Kirichok Y. Acid extrusion from human spermatozoa is mediated by flagellar voltage-gated proton channel. Cell. 2010;140:327–337. doi: 10.1016/j.cell.2009.12.053.
    1. Henkel R., Bittner J., Weber R., Hüther F., Miska W. Relevance of zinc in human sperm flagella and its relation to motility. Fertil. Steril. 1999;71:1138–1143. doi: 10.1016/S0015-0282(99)00141-7.
    1. Wroblewski N., Schill W.-B., Henkel R. Metal chelators change the human sperm motility pattern. Fertil. Steril. 2003;79:1584–1589. doi: 10.1016/S0015-0282(03)00255-3.
    1. Miller M.R., Kenny S.J., Mannowetz N., Mansell S.A., Wojcik M., Mendoza S., Zucker R.S., Xu K., Lishko P.V. Asymmetrically Positioned Flagellar Control Units Regulate Human Sperm Rotation. Cell Rep. 2018;24:2606–2613. doi: 10.1016/j.celrep.2018.08.016.
    1. Kerns K., Morales P., Sutovsky P. Regulation of Sperm Capacitation by the 26S Proteasome: An Emerging New Paradigm in Spermatology. Biol. Reprod. 2016;94:117. doi: 10.1095/biolreprod.115.136622.
    1. Yokota N., Sawada H. Sperm proteasomes are responsible for the acrosome reaction and sperm penetration of the vitelline envelope during fertilization of the sea urchin Pseudocentrotus depressus. Dev. Biol. 2007;308:222–231. doi: 10.1016/j.ydbio.2007.05.025.
    1. Sánchez R., Deppe M., Schulz M., Bravo P., Villegas J., Morales P., Risopatrón J. Participation of the sperm proteasome during in vitro fertilisation and the acrosome reaction in cattle. Andrologia. 2011;43:114–120. doi: 10.1111/j.1439-0272.2009.01031.x.
    1. Chakravarty S., Bansal P., Sutovsky P., Gupta S.K. Role of proteasomal activity in the induction of acrosomal exocytosis in human spermatozoa. Reprod. Biomed. Online. 2008;16:391–400. doi: 10.1016/S1472-6483(10)60601-3.
    1. Ambroggio X.I., Rees D.C., Deshaies R.J. JAMM: A Metalloprotease-Like Zinc Site in the Proteasome and Signalosome. PLOS Biol. 2003;2:e2. doi: 10.1371/journal.pbio.0020002.
    1. Kim I., Kim C.H., Kim J.H., Lee J., Choi J.J., Chen Z.A., Lee M.G., Chung K.C., Hsu C.Y., Ahn Y.S. Pyrrolidine dithiocarbamate and zinc inhibit proteasome-dependent proteolysis. Exp. Cell Res. 2004;298:229–238. doi: 10.1016/j.yexcr.2004.04.017.
    1. Clapper D.L., Davis J.A., Lamothe P.J., Patton C., Epel D. Involvement of zinc in the regulation of pHi, motility, and acrosome reactions in sea urchin sperm. J. Cell Biol. 1985;100:1817–1824. doi: 10.1083/jcb.100.6.1817.
    1. Michailov Y., Ickowicz D., Breitbart H. Zn2+-stimulation of sperm capacitation and of the acrosome reaction is mediated by EGFR activation. Dev. Biol. 2014;396:246–255. doi: 10.1016/j.ydbio.2014.10.009.
    1. Guidobaldi H.A., Cubilla M., Moreno A., Molino M.V., Bahamondes L., Giojalas L.C. Sperm chemorepulsion, a supplementary mechanism to regulate fertilization. Hum. Reprod. 2017;32:1560–1573. doi: 10.1093/humrep/dex232.
    1. Stephenson J.L., Brackett B.G. Influences of zinc on fertilisation and development of bovine oocytes in vitro. Zygote. 1999;7:195–201. doi: 10.1017/S096719949900057X.
    1. Backstrom J.R., Miller C.A., Tokes Z.A. Characterization of neutral proteinases from Alzheimer-affected and control brain specimens: Identification of calcium-dependent metalloproteinases from the hippocampus. J. Neurochem. 1992;58:983–992. doi: 10.1111/j.1471-4159.1992.tb09352.x.
    1. Beek J., Nauwynck H., Maes D., Van Soom A. Inhibitors of zinc-dependent metalloproteases hinder sperm passage through the cumulus oophorus during porcine fertilization in vitro. Reproduction. 2012;144:687–697. doi: 10.1530/REP-12-0311.
    1. Andreychenko S.V., Klepko A.V., Gorban L.V., Motryna O.A., Grubska L.V., Trofimenko O.V. Post-Chornobyl remote radiation effects on human sperm and seminal plasma characteristics. Exp. Oncol. 2016;38:245–251.
    1. Colagar A.H., Marzony E.T., Chaichi M.J. Zinc levels in seminal plasma are associated with sperm quality in fertile and infertile men. Nutr. Res. 2009;29:82–88. doi: 10.1016/j.nutres.2008.11.007.
    1. Dissanayake D., Wijesinghe P.S., Ratnasooriya W.D., Wimalasena S. Effects of zinc supplementation on sexual behavior of male rats. J. Hum. Reprod. Sci. 2009;2:57–61. doi: 10.4103/0974-1208.57223.
    1. Mahajan S.K., Prasad A.S., McDonald F.D. Sexual dysfunction in uremic male: Improvement following oral zinc supplementation. Contrib. Nephrol. 1984;38:103–111.
    1. Prasad A.S., Mantzoros C.S., Beck F.W., Hess J.W., Brewer G.J. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996;12:344–348. doi: 10.1016/S0899-9007(96)80058-X.
    1. Kilic M. Effect of fatiguing bicycle exercise on thyroid hormone and testosterone levels in sedentary males supplemented with oral zinc. Neuro Endocrinol. Lett. 2007;28:681–685.
    1. Underwood E., Somers M. Studies of zinc nutrition in sheep. I. The relation of zinc to growth, testicular development, and spermatogenesis in young rams. Aust. J. Agric. Res. 1969;20:889–897. doi: 10.1071/AR9690889.
    1. Irani M., Amirian M., Sadeghi R., Lez J.L., Latifnejad Roudsari R. The Effect of Folate and Folate Plus Zinc Supplementation on Endocrine Parameters and Sperm Characteristics in Sub-Fertile Men: A Systematic Review and Meta-Analysis. Urol. J. 2017;14:4069–4078.
    1. Hadwan M.H., Almashhedy L.A., Alsalman A.R. Oral Zinc Supplementation Restores Superoxide Radical Scavengers to Normal Levels in Spermatozoa of Iraqi Asthenospermic Patients. Int. J. Vitam. Nutr. Res. 2015;85:165–173. doi: 10.1024/0300-9831/a000235.
    1. Arangasamy A., Venkata Krishnaiah M., Manohar N., Selvaraju S., Guvvala P.R., Soren N.M., Reddy I.J., Roy K.S., Ravindra J.P. Advancement of puberty and enhancement of seminal characteristics by supplementation of trace minerals to bucks. Theriogenology. 2018;110:182–191. doi: 10.1016/j.theriogenology.2018.01.008.
    1. Leitzmann M.F., Stampfer M.J., Wu K., Colditz G.A., Willett W.C., Giovannucci E.L. Zinc Supplement Use and Risk of Prostate Cancer. J. Natl. Cancer Inst. 2003;95:1004–1007. doi: 10.1093/jnci/95.13.1004.
    1. Plum L.M., Rink L., Haase H. The essential toxin: Impact of zinc on human health. Int. J. Environ. Res. Public Health. 2010;7:1342–1365. doi: 10.3390/ijerph7041342.
    1. O’Flaherty C., Fournier D.M. Reactive oxygen species and protein modifications in spermatozoa. Biol. Reprod. 2017;97:577–585. doi: 10.1093/biolre/iox104.
    1. Powell S.R. The antioxidant properties of zinc. J. Nutr. 2000;130:1447S–1454S. doi: 10.1093/jn/130.5.1447S.
    1. Talevi R., Barbato V., Fiorentino I., Braun S., Longobardi S., Gualtieri R. Protective effects of in vitro treatment with zinc, d-aspartate and coenzyme q10 on human sperm motility, lipid peroxidation and DNA fragmentation. Reprod. Biol. Endocrinol. 2013;11:1–10. doi: 10.1186/1477-7827-11-81.
    1. Gualtieri R., Barbato V., Fiorentino I., Braun S., Rizos D., Longobardi S., Talevi R. Treatment with zinc, d-aspartate, and coenzyme Q10 protects bull sperm against damage and improves their ability to support embryo development. Theriogenology. 2014;82:592–598. doi: 10.1016/j.theriogenology.2014.05.028.
    1. Posthuma L., Baerselman R., Van Veen R.P.M., Dirven-Van Breemen E.M. Single and Joint Toxic Effects of Copper and Zinc on Reproduction ofEnchytraeus crypticusin Relation to Sorption of Metals in Soils. Ecotoxicol. Environ. Saf. 1997;38:108–121. doi: 10.1006/eesa.1997.1568.
    1. Barceloux D.G., Barceloux D. Zinc. J. Toxicol. Clin. Toxicol. 1999;37:279–292. doi: 10.1081/CLT-100102426.
    1. Johnson F.O., Gilbreath E.T., Ogden L., Graham T.C., Gorham S. Reproductive and developmental toxicities of zinc supplemented rats. Reprod. Toxicol. 2011;31:134–143. doi: 10.1016/j.reprotox.2010.10.009.
    1. Manzo S., Schiavo S., Oliviero M., Toscano A., Ciaravolo M., Cirino P. Immune and reproductive system impairment in adult sea urchin exposed to nanosized ZnO via food. Sci. Total Environ. 2017;599–600:9–13. doi: 10.1016/j.scitotenv.2017.04.173.
    1. Merrells K.J., Blewett H., Jamieson J.A., Taylor C.G., Suh M. Relationship between abnormal sperm morphology induced by dietary zinc deficiency and lipid composition in testes of growing rats. Br. J. Nutr. 2009;102:226–232. doi: 10.1017/S0007114508159037.
    1. Ding B., Zhong Q. Zinc deficiency: An unexpected trigger for autophagy. J. Biol. Chem. 2017;292:8531–8532. doi: 10.1074/jbc.H116.762948.
    1. Jaiswal B.S., Eisenbach M. Capacitation. In: Hardy D.M., editor. Fertilization. Academic Press; Cambridge, MA, USA: 2002. pp. 57–117.
    1. Aitken R.J., Baker M.A., Nixon B. Are sperm capacitation and apoptosis the opposite ends of a continuum driven by oxidative stress? Asian J. Androl. 2015;17:633–639. doi: 10.4103/1008-682X.153850.
    1. Yi Y.J., Manandhar G., Oko R.J., Breed W.G., Sutovsky P. Mechanism of sperm-zona pellucida penetration during mammalian fertilization: 26S proteasome as a candidate egg coat lysin. Soc. Reprod. Fertil. Suppl. 2007;63:385–408.

Source: PubMed

Sponsorit ja yhteistyökumppanit

Sairaudet

Huumeiden interventiot

3
Tilaa