FSH increases cAMP levels and blocks oocyte-cumulus cell gap junctional communication (GJC).

<p>(A) The biphasic effect of FSH on oocyte maturation. Cumulus-oocyte complexes (COCs) were cultured with or without 50 IU/L FSH in HX medium for 22 h. The rate of GVBD was scored in 2-h intervals during culture. FSH inhibited maturation during the first 8 h of the treatment period and stimulated maturation after 8 h. *<i>P</i><0.01 vs. the control group for that time point. (B) Changes in cAMP levels in cumulus cells of COCs after FSH treatment. (C) Changes in cAMP levels in the oocytes of COCs stimulated with FSH. (D) Cumulus cell-oocyte GJC during FSH-induced <i>in vitro</i> oocyte maturation. COCs were cultured in HX medium containing FSH (open circles) or not containing FSH (filled circles) for various periods of time. Then they were pulsed with calcein-AM, denuded of surrounding cumulus cells, and assessed for intra-oocyte fluorescence. A mean of 10 oocytes were used at each time point in each of three replicate experiments. **<i>P</i><0.05, *<i>P</i><0.01 vs. control.