An insufficient increase of cytosolic free calcium level results postovulatory aging-induced abortive spontaneous egg activation in rat
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The present study was aimed to find out whether postovulatory aging-induced abortive spontaneous egg activation (SEA) is due to insufficient increase of cytosolic free Ca2+ level.
Immature female rats (22–24 days old) were subjected to superovulation induction protocol. Eggs were collected 14, 17 and 19 h post-hCG surge to induce in vivo egg aging. The eggs were collected 14 h post-hCG surge and cultured in vitro for 3, 5 and 7 h to induce in vitro egg aging. The morphological changes, rate of abortive SEA, chromosomal status and cytosolic free Ca2+ levels were analyzed.
Postovulatory aging induced morphological features characteristics of abortive SEA in a time-dependent manner in vivo as well as in vitro. The extracellular Ca2+ increased rate of abortive SEA during initial period of culture, while co-addition of a nifedipine (L-type Ca2+ channel blocker) protected against postovulatory aging-induced abortive SEA. However, CI induced morphological features characteristics of egg activation (EA) in a dose-dependent manner. As compare to control, an increase of cytosolic free Ca2+ level (1.42 times) induced abortive SEA, while further increase of cytosolic free Ca2+ level (2.55 times) induced EA.
Our results show that an insufficient cytosolic free Ca2+ level is associated with postovulatory aging -induced abortive SEA, while furthermore increase is required to induce EA in rat.
KeywordsCytosolic free calcium Abortive spontaneous egg activation Postovulatory aging Rat eggs
The authors are very thankful to Prof. T.G. Shrivastav, Department of Reproductive Biomedicine, National Institute of Health and Family Welfare, Baba Gang Nath Marg, New Delhi-110067, India for providing fluorescence light microscope facility (Nikon, Eclipse; E-80i, Japan).
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