Studies of platelet factor 4 and beta thromboglobulin release during exercise: lack of relationship to myocardial ischemia.

Platelet activation, which results in release of the platelet-specific proteins platelet factor 4 (PF4) and BTG thromboglobulin (BTG), may participate in exercise-induced myocardial ischemia by the formation of intravascular platelet aggregates or the generation of vasoactive substances such as thrombox- ane A2. We sought to determine if platelet release occurs during exercise-induced ntyocardial ischemia and its relationship to exercise-induced catecholamine release in 10 normal males (mean age 29 + 6 years) and 25 males with proved coronary artery disease (mean age 60 8 years) who performed maximal, symptom- limited treadmill exercise tests. None of the subjects took drugs known to modify platelet behavior; 17 coronary artery disease patients took B-blocking agents. Plasma and urine PF4, plasma BTG and plasma catecholamines were measured before and immediately after exercise. Plasma PF4 and BTG were also measured 30 minutes after exercise. Ischemia, defined as angina or 1 mm or more of horizontal or downsloping ST depression, developed in 14 coronary artery disease patients.