Role of the extracellular Ca2+ on the intracellular Ca2+ changes in fertilized and activated mouse oocytes.
Changes in intracellular calcium concentration ([Ca2+]i) in fertilized mouse oocytes were measured using the calcium-sensitive dye, fura-2. After fertilization, an initial long-lasting [Ca2+]i increase was followed by a periodic [Ca2+]i increase. The periodic increase in [Ca2+]i persisted for 1 to 3 h and all fertilized oocytes extruded the second polar body within 4 h. The mean interval of periodic [Ca2+]i increase was 470 +/- 180 s (mean +/- SD). The frequency of the periodic [Ca2+]i increase depended on the extracellular calcium concentration. Verapamil and nifedipine inhibited the periodic [Ca2+]i increase. Sixty-five per cent of tested cells extruded the second polar body within 90 min of exposure to 7% ethanol. In these activated oocytes, the long-lasting [Ca2+]i increase was observed. However, no cells showed a repetitive increase in [Ca2+]i. Both release of calcium from intracellular stores and influx of extracellular calcium contribute to the increase in [Ca2+]i induced by ethanol. We conclude that the extrusion of the second polar body requires an increase in [Ca2+]i above a certain threshold level and the mobilization of calcium of both the intracellular and extracellular space in mouse oocytes.
Shiina
Y
Y
Department of Obstetrics and Gynecology, Yamagata University School of Medicine, Japan.
Kaneda
M
M
Matsuyama
K
K
Tanaka
K
K
Hiroi
M
M
Doi
K
K
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D000431:Ethanol / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D005306:Fertilization / Q000502:physiology*; D016257:Fura-2; D007424:Intracellular Fluid / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D008954:Models, Biological; D009543:Nifedipine / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D015053:Zygote / Q000187:drug effects / Q000378:metabolism*
D000431:Ethanol; D014700:Verapamil; D009543:Nifedipine; D002118:Calcium; D016257:Fura-2