Effect of dopamine on adenosine 3',5'-cyclic monophosphate levels in human platelets.

1. The dopamine effect on intraplatelet adenosine 3',5'-cyclic monophosphate (cAMP) levels was evaluated in healthy subjects. 2. Dopamine levels over 30 nmol/l increased cAMP concentration in a concentration-dependent way. 3. The platelet preincubation with propranolol (beta-adrenoceptor antagonist) prevented the dopamine effect, whereas phentolamine (alpha-adrenoceptor antagonist) failed to modify the platelet response to this catecholamine. Dopamine receptor antagonist domperidone directly increased cAMP levels and it enhanced the dopamine effects. 4. Our results indicate that dopamine effect is mainly mediated by beta-adrenoceptor stimulation.