The effect of exercise on platelet beta-adrenoceptor function and platelet aggregation in healthy human volunteers

Plasma levels of adrenaline and noradrenaline, platelet cyclic-AMP (cAMP) content, platelet aggregation, platelet release of beta-thromboglobulin, and platelet factor 4 and serum content of thromboxane B2(TXB2) and 6-keto-PGF1 alpha were measured in 12 healthy male volunteers (age 38-72, mean 54.2 years) who were tested at rest and immediately after five min light cycle exercise. The plasma levels of adrenaline and noradrenaline increased significantly after exercise (P less than 0.01). The platelet cAMP level was not changed by exercise. The functional capacity of platelet beta-adrenoceptors, determined as cAMP production after beta-adrenoceptor stimulation in vitro, decreased highly significantly after exercise in all 12 volunteers (P less than 0.01). No alteration was observed in platelet aggregation induced by adrenaline or in platelet release of beta-thromboglobulin or platelet factor 4. No change was observed in the serum levels of TXB2 and 6-keto-PGF1 alpha. In conclusion: light cycle exercise results in a decreased functional capacity of platelet beta-adrenoceptors, but has no effect on platelet aggregation or platelet release. This might indicate a concomitant and equal decreased functional capacity of platelet alpha-adrenoceptors.