EXTRACELLULAR ADENOSINE 5'-TRIPHOSPHATE INDUCES CA2+ EFFLUX FROM FRESHLY ISOLATED ADULT RAT CARDIOMYOCYTES - POSSIBLE INVOLVEMENT OF NA+/CA2+ EXCHANGE MECHANISM

摘要

In the present study, we examined the effect of extracellular adenosine 5'-triphosphate (ATP) on Ca2+ efflux from freshly isolated adult rat cardiomyocytes. ATP at 1 mM caused a release of 3.6+/-0.08% of the total cellular content. The Ca-45(2+) efflux from the cells was also stimulated by adenosine-5'-O-(3-thiotriphosphate) (ATP-gamma s), alpha,beta-methylene-ATP and adenosine 5'-diphosphate (ADP), but not by adenosine 5'-monophosphate (AMP) or adenosine. The effect of ATP was inhibited by a known purinergic P-2-receptor antagonist, but not by a P-1-receptor antagonist. From these results, it is conceivable that the effect of ATP on Ca2+ efflux from cardiomyocytes is mediated through P-2-purinoceptars. It was also observed that ATP caused a rise in [Ca2+](i) to almost 200 nM. The ATP-stimulated Ca-45(2+) efflux was not affected by removal of extracellular Ca2+, but was dependent on the presence of extracellular Na+. Moreover, ATP caused a Na-22(+) influx into the cells of about 2.0-fold over the basal value. These results suggest that ATP stimulates extracellular Na+-dependent Ca-45(2+) efflux from freshly isolated adult rat cardiomyocytes, probably through its stimulatory effect on plasma membrane P-2-purinoceptors which may couple to Na+/Ca2+ exchange. [References: 30]