THE EFFECTS OF EXERCISE TRAINING ON RESTING PROSTACYCLIN AND THROMBOXANE A(2) IN OLDER ADULTS

Ten adult volunteers participated in 16 weeks of cardiovascular exerci se training (EG) to determine the effects of training on resting prost acyclin (PGI(2)) and thromboxane A(2) (TXA(2)). Six volunteers of simi lar age served as sedentary controls (CG). Blood was collected in tube s after training and eicosanoids were measured by standard I-125 RIA m ethods. Over the 16 weeks of the study, PGI(2) decreased 48% for EG an d 33% for CG. There were no between-group differences for PGI(2) value s. No significant within-group changes in TXA(2) were found, whereas b etween-group pretraining TXA(2) values were significantly different. A time main effect for PGI(2) may indicate a seasonal shift in this eic osanoid; however, the additional 15% decrease in PGI(2) for EG may be due to a training-induced reduction in PGI(2) substrate and/or endothe lial sensitivity to agonists. The lack of within-group changes in TXA( 2) may be due to a combination of high platelet turnover and a trainin g stimulus inadequate to alter platelet function.