Inhibition of LH-stimulated cyclic AMP formation in pre-ovulatory rat granulosa cells by follicular fluid.
Immature female rats were injected sc with a single dose of PMSG to induce growth and maturation of ovarian follicles. In the morning of prooestrus the rats were given a single ip injection of LH (10 micrograms/rat) or 0.154 M NaCl, 2 h prior to sacrifice. Granulosa cells were isolated fro the pre-ovulatory follicles and incubated in Krebs bicarbonate buffer, for 1 h with or without in vitro addition of various test substances. Following incubation the amounts of cAMP in tissue plus medium were determined. It was found that the isolated granulose cells exposed to LH in vivo responded to the addition of LH in vitro with a production of high amounts of cAMP, i.e. these cells were not refractory to LH stimulation and in fact responded better than granulosa cells isolated from ovaries not exposed to LH in vivo. The addition to the incubation medium of follicular fluid (FFl) obtained from pre-ovulatory follicles decreased the effect of LH in vitro when added at a final concentration of 1% and completely abolished it at a concentration of 3%. Removal of steroids from the FFl did not influence the inhibitory effect and the addition of a phosphodiesterase inhibitor (IBMX) in vitro did not alter the results in principle. These results point to the existence of a factor in the FFl which interacts with the sensitivity of the isolated pre-ovulatory granulosa cells to repeated exposures to LH. Characterization of this factor is subject to further investigations.
D000818:Animals; D001826:Body Fluids / Q000032:analysis; D002478:Cells, Cultured; D003470:Culture Media; D000242:Cyclic AMP / Q000096:biosynthesis*; D005260:Female; D006064:Gonadotropins, Equine / Q000494:pharmacology*; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006080:Ovarian Follicle / Q000032:analysis; D011247:Pregnancy; D011359:Proestrus; D051381:Rats
D003470:Culture Media; D006064:Gonadotropins, Equine; D007986:Luteinizing Hormone; D000242:Cyclic AMP