Alpha 2-adrenoceptors and platelet function in patients with variant angina

Area of Science:

• Cardiology
• Pharmacology
• Molecular Biology

Background:

• Platelets in variant angina patients display hyperactivity to epinephrine.
• The underlying mechanism for this hyperactivity requires further investigation, particularly concerning surface alpha-adrenoceptor status.

Purpose of the Study:

• To investigate the capacity and affinity of alpha-adrenoceptor binding sites on platelets from patients with ischemic heart disease and control subjects.
• To determine if changes in platelet alpha-adrenoceptor status correlate with variant angina.

Main Methods:

• Utilized [3H]dihydroergocryptine, an alpha-antagonist, to assess alpha-adrenoceptor binding capacity and affinity in platelet lysates.
• Compared binding characteristics between 22 patients with ischemic heart disease (including acute myocardial infarction, effort angina, and variant angina) and 13 control subjects.
• Also examined binding capacity for [3H]-rauwolscine, an alpha 2 antagonist, in variant angina patients.

Main Results:

• Patients with variant angina exhibited a significantly higher capacity (49% increase) of platelet alpha-adrenoceptors compared to controls and other ischemic heart disease groups.
• No significant difference in the affinity for [3H]dihydroergocryptine was observed across the groups.
• Increased binding capacity for [3H]-rauwolscine was also noted in variant angina patients.

Conclusions:

• The enhanced reactivity to epinephrine in variant angina patients is likely due to an increased capacity of platelet alpha-adrenoceptors.
• This suggests a specific molecular alteration in platelets contributing to the pathophysiology of variant angina.