Platelet aggregability to platelet activating factor at rest and after exercise in patients with coronary artery disease

The platelet response to the aggregatory effect of platelet-activatingfactor (PAF) in relation to blood PAF levels, serum PAF-acetylhydrolase(PAF-AH) activity and to their lipidoemic profile, was studiedin 44 patients with coronary artery disease undergoing exercisetests. The PAF EC₅₀ values in 21 patients with positive exercisetest results were found to be significantly decreased at restcompared with 21 normal subjects (126±3•9 nM and24•9±11•7 nM respectively) (P<0•0001).Moreover, the maximal percentage of aggregation to 50 nM PAFwas found to be significantly increased (20•0±4•3%vs 13•5±3•6% respectively) (P<0•0001).By contrast, the PAF EC₅₀ values and the maximal percentageof aggregation in 23 patients with negative exercise test resultswere not statistically significantly different from the controlgroup (25•2±11•4 nM and 14•1±4•7%,respectively). At the end of exercise, the PAF EC₅₀ values and the maximalpercentage of aggregation did not change in any group, and therewere no significant differences in the whole-blood PAF levelseither at rest or at the end of exercise. In patients with positiveexercise test results, the PAF-AH activity at rest was significantlyhigher compared with the control group (37•2±8•0nmol. ml^–1. min^–1 vs 32•4±4•3 nmol.ml^–1. min^–1), (P<0•03), whereas the enzymeactivity did not differ in patients with negative exercise testresults compared to controls (33•6±6•1 nmol.ml^–1. min^–1). There was no change in PAF-AH activity during exercise in anygroup. The enzyme activity was positively correlated to theserum total and low density lipoprotein (LDL) cholesterol levelsin the control group and in patients with negative exercisetest results, whereas no correlation was found between PAF-AHactivity and total or LDL cholesterol levels in patients withpositive exercise test results. Our results suggest that platelethyper-reactivity to PAF may play a pathophysiological role inmyocardial ischaemia observed during exercise in coronary arterydisease patients.