Cyclic AMP, Prostaglandin E2 and Steroids: Possible Mediators in the Rat Cumulus Oophorus Mucification

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Abstract
The possible role of cyclic AMP (cAMP), prostaglandin E2, progesterone and estradiol-17β in in vitro induction of the rat cumulus oophorus mucification was studied with the scanning electron microscope. Follicular cumulus-oocyte complexes were isolated at early proestrus and cultured for 24 h. Cyclic AMP levels in the incubated complexes were elevated by addition of cAMP derivatives (dibutyryl cAMP or 8 bromo cAMP), the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (MIX), or the adenylate cyclase stimulator, cholera enterotoxin. Under all these culture conditions the cumulus cells were stimulated to secrete a hyaluronidase-sensitive mucoid material which coated the cumulus-oocyte complexes. These complexes were similar in appearance to those incubated in the presence of gonadotropins. In the absence of the above agents extracellular material was not observed. In vitro cumulus mucification was not induced by prostaglandin E2; indomethacin, an inhibitor of prostaglandin synthetase, failed to block mucification in complexes that have been incubated in the presence of LH. Cumulus complexes were not stimulated to mucify in vitro by progesterone or estradiol-17β. Therefore, the response of the cumulus cells to the gonadotropic stimulus appears to be mediated by cAMP. Prostaglandin E2 and steroids seem not to be involved in this process.