Measurement of Platelet Dense Granule Release in Healthy Volunteers

Aspirin has been shown to reduce cardiovascular events in at risk individuals. Elucidation of mechanisms of aspirin resistance and a possible loss of effect of aspirin over time with chronic aspirin treatment necessitate a more precise method of measuring the "release phase" of platelet activation, including the release of dense granules from platelets.

Study Overview

• Status: Withdrawn
• Conditions: Platelet Aggregation
• Intervention / Treatment: Drug: Aspirin

Detailed Description

This is a proposal for a pilot study to evaluate the feasibility of measuring 5-hydroxytryptamine (5-HT) release from platelets as an indicator of dense granule release during platelet activation in volunteers taking aspirin.

One phase of platelet response to activating agonists involves release of dense granules, which are known to contain 5HT (serotonin) and ATP. There are various methods of measuring the degranulation of platelets: ATP release can be measured using a lumiaggregometer, and release of 14C radiolabeled 5-HT from platelets. Using the aggregometer and a 14C labeled 5-HT assay can be used to measure 5-HT release from platelets.

Our experience suggests that ADP-induced ATP release is insensitive to detect very low levels of platelet dense granule release, which occurs in aspirin-treated subjects. The pilot study will permit optimizing the method for reliably detecting low levels of 5HT release in patients who achieve submaximal inhibition of the cyclooxygenase during aspirin treatment.

• Study Type: Interventional
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Tennessee
    • Nashville, Tennessee, United States, 37232
      • Vanderbilt University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: Male

Description

Inclusion Criteria:

• Males over age 18
• Non-smokers
• No chronic medical illness
• No chronic medications

Exclusion Criteria:

• ASA/NSAID use previous 14 days.
• History of chronic NSAID use.
• Currently taking NSAIDs, opioid analgesics, corticosteroids, or anticoagulants.
• History of coronary artery disease, myocardial infarction, coronary artery bypass grafting, percutaneous angioplasty, diabetes mellitus or stroke.
• History of hypertension
• BMI >35
• Smokers
• History of gastric, duodenal, or esophageal ulcers or serious gastrointestinal bleed.
• History of frequent headaches, pain syndrome, or other condition requiring frequent use of analgesics.
• History of adverse reaction to ASA.
• Initial platelet count <100K/µl or >500K/µl.
• Initial hematocrit <35% or >50%.
• Weight less than 110 pounds.

Female subjects will be excluded to avoid possible confounding uterine smooth muscle production of prostaglandins which various throughout the menstrual cycle.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: 40 mg non-enteric coated aspirin; 40 mg non-enteric coated ASA once daily for 21 + or - 2 days	Drug: Aspirin; 40 mg non-enteric coated ASA once daily for 21 + or - 2 days

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
The primary measurement will be platelet 5-HT release induced by ADP after 1 and 2 weeks administration of daily ASA.	3 weeks

Secondary Outcome Measures

Outcome Measure	Time Frame
Measurements will include platelet COX-1 activity, flow cytometric measurement of markers of platelet activation, platelet aggregation and ATP release, and serum thromboxane B2 (TxB2) levels, at each timepoint.	3 weeks

Collaborators and Investigators

• Sponsor: Vanderbilt University
• Investigators: Principal Investigator: John A Oates, M.D., Vanderbilt University

Study record dates

Study Major Dates

• Study Start: July 1, 2009
• Primary Completion (Actual): June 1, 2012
• Study Completion (Actual): June 1, 2012

Study Registration Dates

• First Submitted: July 17, 2009
• First Submitted That Met QC Criteria: July 20, 2009
• First Posted (Estimate): July 21, 2009

Study Record Updates

• Last Update Posted (Estimate): December 7, 2015
• Last Update Submitted That Met QC Criteria: December 4, 2015
• Last Verified: December 1, 2015

More Information

Terms related to this study

• Keywords: platelet aggregation; granule secretion; thromboxane production; platelet activation; aspirin resistance; cyclooxygenase-1; flow cytometry; ATP release; Platelet aggregation in healthy volunteers
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Molecular Mechanisms of Pharmacological Action; Peripheral Nervous System Agents; Enzyme Inhibitors; Analgesics; Sensory System Agents; Anti-Inflammatory Agents, Non-Steroidal; Analgesics, Non-Narcotic; Anti-Inflammatory Agents; Antirheumatic Agents; Fibrinolytic Agents; Fibrin Modulating Agents; Platelet Aggregation Inhibitors; Cyclooxygenase Inhibitors; Antipyretics; Aspirin
• Other Study ID Numbers: IRB# 080895; NIH/NHLBI #81009