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-activating factor (PAF) in relation to blood PAF levels serum PAF-acetylhydrolas e (PAF-AH) activity and to their lipidaemic profile, was studied in 34 patients with coronary artery disease undergoing exercise tests. The PAF EC(50) values in 21 patients with positive exercise test results w ere found to be significantly decreased at rest compared with 21 norma l subjects (12.6 +/- 3.9 nM and 24.9 +/- 11.7 nM respectively) (P < 0. 0001). Moreover, the maximal percentage of aggregation to 50 nm PAF wa s found to be significantly increased (20.0 +/- 4.3% vs 13.5 +/- 3.6%, respectively) (P < 0.0001). By contrast, the PAF EC(50) values and th e maximal percentage of aggregation in 23 patients with negative exerc ise test results were not statistically significantly different from t he control group (25.2 +/- 11.4 nM and 14.1 +/- 4.7%, respectively. At the end of exercise, the PAF-EC(50) values and the maximal percentage of aggregation did not change in any group, and there were no signifi cant differences in the whole-blood PAF levels either at rest or at th e end of exercise. In patients with positive exercise test results, th e PAF-AH activity, at rest was significantly higher compared with the control group (37.2 +/- 8.0 nmol. ml(-1). min(-1) vs 32.4 +/- 4.3 nmol . ml(-1). min(-1)), (P < 0.03), whereas the enzyme activity did not di ffer in patients with negative exercise test results compared to contr ols (33.6 +/- 6.1 nmol. ml(-1). min(-1)). There was no change in PAF-A H activity during exercise in any group. The enzyme activity was posit ively correlated to the serum total and low density lipoprotein (LDL) cholesterol levels in the control group and in patients ,vith negative exercise test results, whereas no correlation was found between PAF-A H activity, and total or LDL cholesterol levels in patients, with posi tive exercise test results. Our results suggest that platelet hyper-re activity to PAF may, play a pathphysiological role in myocardial ischa emia observed during exercise in coronary artery, disease patients.