EFFECTS OF SHORT-TERM EXERCISE ON FEMALE PLATELET-FUNCTION DURING DIFFERENT PHASES OF THE MENSTRUAL-CYCLE

Previous studies have shown that premenopausal women have a low incide nce of cardiovascular diseases, and that acute exercise affects male p latelet function in an intensity-dependent manner. To investigate whet her acute exercise affects female platelet function differently from m ales, sixteen sedentary women in the midfollicular phase or midluteal phase received strenuous or moderate exercise on a bicycle ergometer. Before and immediately after exercise, platelet adhesiveness, adenosin e diphosphate-induced platelet aggregation and intracellular calcium c oncentration elevation, platelet cAMP and cGMP contents, urinary 11-de hydro-TXB2 and 6-keto-prostaglandin F1 alpha levels, and plasma nitric oxide metabolite level were determined. Our results showed no differe nces in exercise performance and in resting platelet function between two menstrual phases, with little change in urinary eicosanoid metabol ites and platelet cAMP levels under all experimental conditions. In ad dition, for women in the midfollicular phase, (1) strenuous exercise i ncreased platelet adhesiveness, adenosine-diphosphate-induced platelet aggregation, and intracellular calcium concentration elevation, where as moderate exercise suppressed them; (2) moderate exercise enhanced p lasma nitric oxide metabolite and platelet cGMP levels. In contrast, n one of these platelet functions was affected by acute exercise in the midluteal phase. Therefore, we conclude that acute exercise affects fe male platelet function in an intensity-dependent manner in the midfoll icular phase but not in the midluteal phase. The irresponsiveness of p latelets to acute exercise in the luteal phase may partially explain w hy premenopausal women have a lower incidence of cardiovascular diseas es than men.