Inhibitory action of cyclic guanosine 5'-phosphoric acid (GMP) on oocyte maturation: dependence on an intact cumulus.
Oocyte cumulus complexes (OCC) were isolated from antral follicles of proestrous hamsters prior to the luteinizing hormone (LH)/follicle-stimulating hormone (FSH) surge and then incubated from 4 to 24 h at 37 degrees C. Under these conditions approximately 89% of the oocytes exhibited metaphase plates (11% were in the dictyate stage) and addition of LH (200 ng/ml ovine NIH-LH-S20) did not significantly alter the percentage of oocyte maturation. Approximately 50% of the OCC incubated for 24 h with 6 mM 8-bromo-cyclic quanine 3':5' monophosphate (8-Br-cGMP) were prevented from maturing beyond the dictyate stage. OCC incubated with 6 mM 8-bromo-cyclic adenosine 3':5' monophosphate (8-Br-cAMP) were also prevented from maturing (59.5% 8-Br-cAMP) in vitro. LH (200 ng/ml) was able to overcome the 8-Br-cAMP-induced inhibition of oocyte maturation in OCC. It also produced a decrease in 8-Br-cGMP mediated inhibition which was more pronounced when the dosage of LH was increased to 10 microgram/ml. 8-Br-cGMP prevented oocyte maturation in a dose and time dependent manner. Only 8-Br-cAMP prevented maturation (approximately 60% inhibition) of denuded oocytes in vitro. Denuded oocytes incubated with and without 8-Br-cGMP exhibited no inhibited of maturation. These results indicate that 8-Br-cGMP may exert its inhibitory effects through the cumulus cells. On the other hand, cAMP appears to directly inhibit oocyte maturation.
D015124:8-Bromo Cyclic Adenosine Monophosphate; D000818:Animals; D006224:Cricetinae; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007986:Luteinizing Hormone / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development*; D010063:Ovum / Q000254:growth & development*; D013997:Time Factors
D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D007986:Luteinizing Hormone; D000242:Cyclic AMP; D006152:Cyclic GMP