Hubbard, Christopher J.
M.S. (Master of Science)
Department of Biological Sciences
Meiosis||Follicle-stimulating hormone||Cyclic guanylic acid||Cytochemistry||Phosphatases
Within the mammalian follicle the oocyte is arrested in prophase I of meiosis; following the preovulatory gonadotropin surge, meiosis continues to metaphase of the second meiotic division. Follicular cAMP levels increase in vivo following the gonadotropin surge. Current liturature suggests that cAMP has a dual role in the resumption of meiosis. A rise in cAMP levels within the follicular cells may serve as an initial trigger for resumption, but persistently elevated levels inhibit maturation. When the elevated cAMP levels are allowed to fall, maturation continues. Cyclic GMP has been shown to increase in granulosa cells in response to FSH stimulation. However, well-characterized roles for cGMP in biological processes have yet to be revealed. Both FSH and cGMP have been demonstrated to stimulate cAMP-phosphodiesterase (cAMP-PDE) activity. The purpose of this study is to determine whether FSH (via cGMP) stimulates cAMP-PDE activity, lowers cAMP levels, and affects the spontaneous maturation rate of isolated hamster oocytes, incubated within their cumulus mass. FSH (2 hr exposure), increased cAMP and inhibited maturation in cultured cumulus-oocyte complexes (COCs). Following a longer exposure period (3 hr) FSH-stimulated cAMP decreased, and the maturation rate rose compared with controls. Cyclic GMP elevating agents reduced the inhibitory effects of FSH on maturation and lowered the cAMP content of COCs (2 hr exposure). FSH and other experimental additives increased COC cGMP in a dose and time dependent manner. Both FSH and 8-Br-cGMP stimulated cAMP-PDE activity in a dose dependent manner. Reducing the cGMP concentration, or inhibiting protein synthesis, negated the stimulatory effects of FSH or 8-Br-cGMP on cAMP-PDE activity and maturation. In the intact animal, an increase in LH and FSH stimulates a rise in follicular cAMP and the initiation of maturation. FSH (via cGMP) may serve to decrease high cAMP concentrations and permit maturation to proceed.
Price, Joel S., "The effects of follicle-stimulating hormone and guanosine 3':5' cyclic monophosphate on cAMP-phosphodiesterase and resumption of meiosis in hamster cumulus-oocyte complexes" (1988). Graduate Research Theses & Dissertations. 5646.
v, 73 pages
Northern Illinois University
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