ATRIAL-NATRIURETIC-PEPTIDE STIMULATES NA-DEPENDENT CA2+ EFFLUX FROM FRESHLY ISOLATED ADULT-RAT CARDIOMYOCYTES()

In the present study, we examined the effect of atrial natriuretic pep tide (ANP) on Ca2+ efflux from freshly isolated adult rat cardiomyocyt es, Rat ANP(1-28) stimulated the efflux of Ca-45(2+) from the cells in a concentration-dependent manner (10(-8) M to 10(-6) M). The Ca-45(2) efflux was not affected by removal of extracellular Ca2+, but was de pendent on the presence of extracellular Na+, In addition, rat ANP(1-2 8) caused Na-22(+) influx into the cells, The Ca-45(2+) efflux was als o stimulated by C-type natriuretic peptide-22 (CNP-22), but not by rat brain natriuretic peptide-45 (BNP-45), It was also observed that both rat ANP(1-28) and CNP-22 stimulated guanosine 3',5'-cyclic monophosph ate production within the cells, These results indicate that ANP stimu lates Nac-dependent Ca-45(2+) efflux from freshly isolated adult rat c ardiomyocytes, probably through Na+/Ca2+ exchange, and that the stimul atory effect of ANP on Ca2+ efflux may be mediated via the natriuretic peptide receptor which has been shown to couple to guanylate cyclase, Since it is reported that Na+/Ca2+ exchange is important in calcium h omeostasis within cells, ANP may play a role in the extrusion of intra cellular Ca2+ from isolated adult rat cardiomyocytes. (C) 1997 Federat ion of European Biochemical Societies.