Combined effects of calcium and dibutyryl cyclic AMP on germinal vesicle breakdown in the mouse oocyte

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Authors:
R. D. Powers
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G. A. Paleos
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DOI:
https://doi.org/10.1530/jrf.0.0660001
Volume/Issue:
Volume 66: Issue 1
Page Range:
1–8
Article Type:
Research Article
Online Publication Date:
Sep 1982
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Summary. Mouse oocytes were cultured in the presence of dibutyryl cyclic AMP (dbcAMP) and various agents that affect cytoplasmic calcium concentrations. Treatments that inhibited calcium uptake potentiated the inhibitory effect of dbcAMP and treatments which stimulated cellular calcium uptake overcame the effect of dbcAMP. Elevated extracellular calcium (>10 mm) significantly decreased the inhibitory effect of concentrations of dbcAMP up to 150 μ when compared to control levels of calcium (1·7 mm). In addition, the calcium ionophore A23187 (>1 μm) significantly overcame the effect of dbcAMP in media that contained 1·7 or 20 mm calcium. In the presence of 41 μm-dbcAMP the calcium antagonist verapamil increased (in a dose-dependent fashion) the percentage of oocytes blocked at the germinal vesicle stage, from 21% with 10 μm-verapamil to 99% with 200 μm. A similar dose-dependent, reversible potentiation of the effect of dbcAMP was found with tetracaine, which also lowers cytoplasmic calcium concentrations. These results suggest that a minimum level of cytoplasm calcium is required for the initiation of germinal vesicle breakdown and that the action of dbcAMP is mediated by its effect upon this calcium.

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Print ISSN:
1470-1626
Online ISSN:
1741-7899