Increased prostacyclin production during exercise in untrained and trained men: effect of low-dose aspirin

The influence of a submaximal exercise on urinary 2,3-dinor-6-ketoprostaglandin F1 alpha (2,3-dinor-6-keto-PGF1 alpha), 2,3-dinor-thromboxane B2 (2,3-dinor-TxB2), and prostaglandin E2 excretion and on platelet aggregation was compared in untrained and trained subjects before and after low-dose aspirin administration (50 mg/day, 7 days). 2,3-Dinor-TxB2 excretion was significantly higher in the athletes at rest (P < 0.05). Submaximal exercise selectively increased 2,3-dinor-6-keto-PGF1 alpha excretion without affecting 2,3-dinor-TxB2 or prostaglandin E2 excretion rates or platelet aggregation. Low-dose aspirin inhibited platelet aggregation and 2,3-dinor-TxB2 excretion but reduced 2,3-dinor-6-keto-PGF1 alpha by only 24% in the untrained and by 51% in the trained subjects (P < 0.05). After low-dose aspirin administration, the selective stimulatory effect of submaximal exercise on urinary 2,3-dinor-6-keto-PGF1 alpha excretion was even more pronounced than before. The ratio of 2,3-dinor-6-keto-PGF1 alpha to 2,3-dinor-TxB2 was increased by exercise; this effect was significantly enhanced by low-dose aspirin (P < 0.05). Our results suggest that the stimulatory effect of submaximal exercise on prostacyclin production is mostly due to an activation of prostacyclin synthesis from endogenous precursors rather than the result of an enhanced endoperoxide shift from activated platelets to the endothelium. This effect is potentiated by low-dose aspirin pretreatment, indicating that 50 mg/day of aspirin do not impair exercise-induced endothelial prostacyclin production.