Regulation of intracellular calcium in the mouse egg: evidence for inositol trisphosphate-induced calcium release, but not calcium-induced calcium release.
Fertilization of the mammalian egg initiates transient and repetitive release of Ca2+ from intracellular stores. The mechanism by which these Ca2+ transients are produced is not completely known. We examined the role of two principal Ca2+ release mechanisms, inositol trisphosphate-induced Ca2+ release and Ca(2+)-induced Ca2+ release, in altering intracellular Ca2+ in the mouse egg. Microinjection of inositol 1,4,5-trisphosphate (IP3) transiently elevated intracellular Ca2+ and, at higher concentrations, produced repetitive Ca2+ transients. Addition of 100 microM thimerosal, a sulfhydryl reagent, caused repetitive Ca2+ transients. IP3 and thimerosal responses were inhibited by prior injection of heparin, a competitive antagonist of IP3-induced Ca2+ release. Addition of caffeine or injection of caffeine, ryanodine, or cyclic ADP-ribose, which are known to initiate or modulate Ca(2+)-induced Ca2+ release in sea urchin eggs and other cells, produced no change in intracellular Ca2+. The response to injection of Ca2+ was not altered by prior injection of ryanodine. The magnitude of the Ca2+ transients produced by injection of IP3 was not changed by prior injection of cyclic ADP-ribose or external caffeine. We found no evidence of Ca(2+)-induced Ca2+ release from ryanodine- or caffeine-sensitive stores. It is most likely that release of Ca2+ from intracellular stores in the mouse egg is dependent on IP3-induced Ca2+ release.
Kline
J T
JT
Department of Biological Sciences, Kent State University, Ohio 44242.
Kline
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D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002122:Calcium Chloride / Q000494:pharmacology; D036563:Cyclic ADP-Ribose; D005260:Female; D005307:Fertilization in Vitro; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D008297:Male; D051379:Mice; D010063:Ovum / Q000187:drug effects / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology; D013849:Thimerosal / Q000494:pharmacology; D013997:Time Factors
D036563:Cyclic ADP-Ribose; D012433:Ryanodine; D000246:Adenosine Diphosphate Ribose; D013849:Thimerosal; D002110:Caffeine; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002122:Calcium Chloride; D002118:Calcium