Endothelium-dependent effect of bradykinin and ATP on rabbit ventricular myocytes.

ABSTRACT

We have investigated the effects of bradykinin (BK) and ATP on Ca2+ transient induced by electrical-field stimulation in freshly isolated rabbit ventricular myocytes, in the presence or absence of rabbit aortic endothelial cells. BK and ATP induced an increase in intracellular Ca2+ concentration ([Ca2+]i) in the endothelial cells, but had no significant effect on Ca2+ transient in electrical-field stimulated ventricular myocytes. In the presence of cultured endothelial cells, the amplitude of Ca2+ transient induced by electrical stimulation in ventricular myocytes was decreased. BK and ATP further reduced the amplitude of Ca2+ transient induced by electrical stimulation in ventricular myocytes. These data show that BK and ATP have endothelium-dependent depressing effects on ventricular myocytes and indicate that substances released from endothelial cells in response to BK and ATP stimulation can modulate ventricular myocytes excitation-contraction coupling. However, identification of the cardioactive mediators produced by the endothelial cells requires further study.