Ca2+ release and InsP3 production in avian uterine cells: effects of PGF2 alpha and AVT.
Primary cultures of smooth muscle cells isolated from the shell gland ("uterus") of the domestic hen were permeabilized with digitonin and loaded with 45Ca2+ in the presence of ATP. When these cells were stimulated with prostaglandin F2 alpha (PGF2 alpha), arginine vasotocin (AVT), or D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3], there was a rapid, biphasic, and dose-related release of 45Ca2+ from nonmitochondrial pools. 2-Nitro-4-carboxyphenyl-N,N-diphenylcarbamate, an inhibitor of phospholipase C, had no effect on PGF2 alpha - and Ins(1,4,5)P3-promoted 45Ca2+ efflux, whereas it significantly inhibited AVT-stimulated and a stable analogue of GTP-stimulated 45Ca2+ release. In fura-2-loaded intact cells, both PGF2 alpha and AVT increased intracellular Ca2+ levels [( Ca2+]i) in a dose-related manner in the presence of extracellular Ca2+. However, omission of extracellular Ca2+ prevented a PGF2 alpha, but not AVT-induced, rise in [Ca2+]i In D-myo-[3H]inositol-labeled cells, 10 nM AVT caused a rapid, two- to threefold increase in [3H]-Insp3, whereas PGF2 alpha up to 1 microM was infective. Raising PGF2 alpha to 10 microM increased total inositol phosphates by 22% over controls (P less than 0.05). These results point to marked differences in the mechanisms by which AVT and PGF2 alpha regulate [Ca2+]i in uterine smooth muscle cells. It is suggested that the two agonists act in concert to initiate oviposition.
Molnár
M
M
Department of Obstetrics and Gynecology, St. Louis University School of Medicine, Missouri 63104.
Hertelendy
F
F
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002645:Chickens; D015237:Dinoprost / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D007294:Inositol / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism* / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D007700:Kinetics; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D012430:Ruthenium Red / Q000494:pharmacology; D014599:Uterus / Q000187:drug effects / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology; D014668:Vasotocin / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology
D007295:Inositol Phosphates; D012430:Ruthenium Red; D014638:Vanadates; D007294:Inositol; D015544:Inositol 1,4,5-Trisphosphate; D015237:Dinoprost; D014700:Verapamil; D002118:Calcium; D014668:Vasotocin