Development of calcium releasing activity induced by inositol trisphosphate and cyclic ADP-ribose during in vitro maturation of sea urchin oocytes.
During fertilization of sea urchin eggs, the cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) transiently increases (Ca(2+) transient). Increased [Ca(2+)](i) results from a rapid release from intracellular stores, mediated by one or both of two signaling pathways; inositol 1,4,5-trisphosphate (IP(3)) and IP(3) receptor (IP(3)R) or cyclic GMP (cGMP), cyclic ADP-ribose (cADPR) and ryanodine receptor (RyR). During fertilization, cGMP and cADPR increase preceding the Ca(2+) transient, suggesting their contribution to this. If the RyR pathway contributed to the Ca(2+) transient, its Ca(2+) releasing activity would develop in parallel with that of the IP(3) system during maturation of oocytes. Sea urchin oocytes were cultivated in vitro and Ca(2+) transients induced by photolysis of caged IP(3) or caged cADPR were measured during maturation. Oocytes spontaneously began to maturate in seawater. More than 50% of oocytes underwent germinal vesicle breakdown within 25 h and the second meiosis within 35 h, but it took more than 24 h until they became functionally identical to in vivo-matured eggs. Both IP(3) and cADPR induced Ca(2+) transients comparable to those of in vivo-matured eggs later than 24 h from the second meiosis. However, cADPR induced a small Ca(2+) transient even before meiosis, whereas IP(3) and sperm almost did not.
Miyata
Ken
K
Department of Environmental Biology and Chemistry, Faculty of Science, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan.
Nakano
Takashi
T
Kuroda
Ritsu
R
Kuroda
Hideyo
H
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D036563:Cyclic ADP-Ribose; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism / Q000502:physiology*; D012617:Sea Urchins; D013084:Sperm-Ovum Interactions
D053496:Inositol 1,4,5-Trisphosphate Receptors; D036563:Cyclic ADP-Ribose; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium