Na+-dependent release of intracellular Ca2+ induced by purinoceptors in parotid acinar cells of the rat.
In rat parotid acinar cells, ATP caused a transient increase in the intracellular Ca2+ concentration ([Ca2+]i) in the absence of external Ca2+. The ATP-induced Ca2+ response was strongly suppressed by removal of external Na+. The sequence of potency in increasing [Ca2+]i was 3'-o-(4-benzoyl) benzoyl-ATP > ATP > uridine 5'-triphosphate (UTP). Adenosine, AMP, ADP or alpha,beta-metylene ATP did not cause an increase in [Ca2+]i. The 3'-o-(4-benzoyl) benzoyl-ATP-induced increase in [Ca2+]i was abolished by removal of external Na+, but the UTP-induced response was not. The threshold external Na+ concentration required for ATP- or 3'-o-(4-benzoyl) benzoyl-ATP-induced Ca2+ release was 10-20 mM. ATP but not UTP caused a rise in the intracellular Na+ concentration ([Na+]i). Ca2+ release stimulated by caffeine or treatment with ryanodine reduced the Ca2+ release evoked by ATP. These results suggest that ATP, acting through P2Z purinoceptors, causes Na+ entry by opening cation-permeable channels, and thereafter the increase in [Na+]i triggers Ca2+ release from ryanodine-sensitive stores. UTP, acting through P2U purinoceptors, causes Ca2+ release independent of external Na+.
Fukushi
Y
Y
Department of Physiology, Tohoku University School of Medicine, Sendai, Japan.
Ozawa
T
T
Kanno
T
T
Wakui
M
M
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D008297:Male; D010306:Parotid Gland / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058486:Receptors, Purinergic P2X7; D012433:Ryanodine; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology
C546470:P2rx7 protein, rat; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D012433:Ryanodine; D002110:Caffeine; D000255:Adenosine Triphosphate; D012964:Sodium; D002118:Calcium; D014544:Uridine Triphosphate