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KMID : 0358219960230030357
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Korean Journal of Fertility and Sterility
1996 Volume.23 No. 3 p.357 ~ p.366
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of Calcium in the Oocyte Maturation of Rat
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Abstract
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The present experiments aimed to investigate the metabolism of calcium during oocyte maturation in rat. The concentration of free calcium and calmodulin in oocytes was measured ultrastructural localization of calcium precipitates in oocytes was
observed
with the transmission electron microscope.
Cumulus-free immature oocytes (GV-oocyte) were cultured in vitro through 15 hours. The free calcium concentration in GV oocyte was 55.9±3.5nM. In calcium-containing medium, the free calcium concentration was increased in germinal vesicle
breakdown
(GVBD) oocyte (64.2±7.3nM). In normal medium after calcium chelator treatment (10μM BAPTA/AM) , the free calcium contents were slightly lower than those in control group. In calcium-free medium, the free calcium content was drastically
increased
in
GVBD (72.7±3.4nM) and metaphase Ⅰanaphase Ⅰ (88.0±3.4nM) oocyte. In maturation rate of oocytes, GVBD rate was high in control group (82.9±6.55%) and calcium chelator treatment group (91.2±4.4%), but in calcium-free medium group, it was low
and
then the oocyte was degenerated without polar body formation. Relative content of calmodulin in oocyte was significantly (P<0.001) increased in metaphase Ⅰ-anaphase Ⅰ than in GV and GVBD oocyte. The calcium precipitates were observed in
mitochondria
and cytoplasm of GV oocyte but that were not observed in mitochondria of GVBD and metaphase Ⅰ-anaphase Ⅰ oocyte. And then the calcium precipitates reappeared in mitochondria of metaphase Ⅱ oocyte.
The above results indicate that changes in free calcium and calmodulin concentration of oocyte occur according to the maturational stages and the extracellular calcium is required during oocyte maturation. Also change of calcium localization in
oocyte
occurs according to the maturational stages.
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KEYWORD
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