The role of epidermal growth factor in platelet-endothelium interactions

The objective of this study was to determine whether endogenous EFG released after submaximal physical exercise, affects platelet-endothelium interactions. Sixteen healthy male volunteers, aged 23-26 years, were submitted to a submaximal bicycle ergometry test. Blood for determination of EGF concentrations, platelet function studies (concentrations of beta-TG, PF4 and TXB2) and endothelium activity (LTC4 and endothelin-1,2 concentrations) was taken via an intravenous catheter before starting exercise and 15, 30 and 60 min after. A similar scheme was followed to investigate changes in the same parameters induced by a slow intravenous infusion of 0.3 mg/kg b.w. phentolamine (an alpha-adrenergic blocker) before exercise. Plasma concentrations of EGF and the markers of platelet function-beta-TG and PF4 as well as LTC4 concentrations increased only 15 min following exercise. The concentrations of TXB2, and endothelium-1,2 were almost unchanged 15 min after the submaximal bicycle ergometry test. Phentolamine markedly decreased the EGF concentrations in plasma (15 min following exercise) while at 30 and 60 min after exercise it had no effect on this parameter. No significant changes in concentrations of beta-TG, PF6, LTC4 and endothelin-1,2 after phentolamine infusion were found. These results show that increase of plasma EGF following exercise was accompanied with increase of beta-TG, PF4 and LTC4 concentrations. Inhibition of alpha-adrenergic receptors with phentolamine abolished the exercise-induced increase in plasma EGF concentration. The findings suggest that endogenous EGF may affect the platelet function and changes the reactivity of the vascular endothelium.