Fig. 15. A diagram of the hypothetical mechanism for the cyclic AMP (cAMP) inhibition of germinal vesicle breakdown (GVBD) or resumption of meoisis. Follicle-stimulating hormone (FSH) receptor signal transduction in the granulosa cells leads to increased cAMP production. The cAMP can diffuse through the granulosa-oocyte connexin-37 (C×37) gap junctions, where it accumulates at high levels in the ooplasm to inhibit the breakdown (BD) of the germinal vesicle (GV) ( i.e. inhibits the resumption of meiosis or GVBD).