Extracellular adenosine 5'-triphosphate induces Ca2+ efflux from freshly isolated adult rat cardiomyocytes: possible involvement of Na+/Ca2+ exchange mechanism.
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 45Ca2+ 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 P2-receptor antagonist, but not by a P1-receptor antagonist. From these results, it is conceivable that the effect of ATP on Ca2+ efflux from cardiomyocytes is mediated through P2-purinoceptors. It was also observed that ATP caused a rise in [Ca2+]i to almost 200 nM. The ATP-stimulated 45Ca2+ efflux was not affected by removal of extracellular Ca2+, but was dependent on the presence of extracellular Na+. Moreover, ATP caused a 22Na+ influx into the cells of about 2.0-fold over the basal value. These result suggest that ATP stimulates extracellular Na+-dependent 45Ca2+ efflux from freshly isolated adult rat cardiomyocytes, probably through its stimulatory effect on plasma membrane P2-purinoceptors which may couple to Na+/Ca2+ exchange.
Hori
T
T
Department of Cardiovascular Surgery and Pharmacology, School of Medicine, The University of Tokushima, Japan.
Yoshizumi
M
M
Kitagawa
T
T
Houchi
H
H
Tamaki
T
T
Katoh
I
I
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D017136:Ion Transport; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D013498:Suramin / Q000494:pharmacology
D019831:Sodium-Calcium Exchanger; D013498:Suramin; D000584:Amiloride; D000255:Adenosine Triphosphate; D012964:Sodium; D002118:Calcium