Multiple stores of calcium are released in the sea urchin egg during fertilization.
Fertilization initiates a transient increase in intracellular Ca2+ principally by Ca2+ release from intracellular stores. Possible multiple Ca2+ stores and multiple receptor regulation of the same store have been reported. Here we report the presence of at least two independent intracellular Ca2+ stores in the sea urchin egg, which are released during fertilization. Ca2+ release from one store is mediated by inositol 1,4,5-trisphosphate (IP3) and is sensitive to low molecular weight heparin. The other store is heparin insensitive and independent of IP3 regulation, but the regulatory factor remains unidentified. A transient increase in Ca2+ in heparin-loaded eggs is observed during fertilization, which suggests that IP3-independent Ca2+ release mediates the production of IP3 and release of the IP3-dependent store. Experiments presented here do not support the idea of sperm receptor coupling to inositol phospholipid hydrolysis through a GTP-binding protein mediating the fertilization response.
Rakow
T L
TL
Department of Zoology, Iowa State University, Ames 50011.
Shen
S S
SS
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005260:Female; D005306:Fertilization; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D010063:Ovum / Q000187:drug effects / Q000502:physiology*; D012617:Sea Urchins; D013094:Spermatozoa / Q000502:physiology
D016244:Guanosine 5'-O-(3-Thiotriphosphate); D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002118:Calcium