{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,3]],"date-time":"2026-04-03T16:00:07Z","timestamp":1775232007170,"version":"3.50.1"},"reference-count":37,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[2005,4,25]],"date-time":"2005-04-25T00:00:00Z","timestamp":1114387200000},"content-version":"vor","delay-in-days":6416,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Exp. Zool."],"published-print":{"date-parts":[[1987,10]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>In the amphibian ovarian follicle, progesterone production is thought to induce maturation of the enclosed oocyte. Intracellular mechanisms regulating these events in the somatic and germ cells are incompletely understood. However, calcium appears to play a role in the production and action of progesterone. Experiments using calcium antagonists were carried out to delineate the role of extra\u2010 and intracellular calcium during in vitro stimulation of follicular steroidogenesis and oocyte maturation. Calcium\u2010free medium, verapamil, and La<jats:sup>3+<\/jats:sup> were used to block Ca<jats:sup>2+<\/jats:sup> influx and inhibited follicular progesterone accumulation in response to frog pituitary homogenate (FPH) or exogenous cAMP + IBMX. Progesterone accumulation was not impaired under identical conditions when pregnenolone was added to cultured follicles. TMB\u20108, an inhibitor of intracellular Ca<jats:sup>2+<\/jats:sup> mobilization, partially inhibited progesterone levels stimulated by FPH at low doses but not higher doses of the inhibitor. However, TMB\u20108 inhibited FPH\u2010induced oocyte germinal vesicle breakdown (GVBD) in a dose\u2010dependent manner, as well as maturation due to exogenous progesterone or La<jats:sup>3+<\/jats:sup>. Calmodulin antagonists, W\u20107, R24571, and trifluoperazine, were used to assess the involvement of calmodulin in the responses of these two cell types. All three antagonists inhibited progesterone accumulation induced by FPH with the apparent order of potency being R24571 &gt; W\u20107 &gt; TFP. W\u20107 inhibited cAMP\u2010induced progesterone elevation, but had no effect on conversion of pregnenolone to progesterone. Of these three calmodulin antagonists, only R24571 exhibited a dramatic ability to inhibit GVBD induced by exogenous progesterone and was associated with morphologic alterations in the oocytes. These data suggest that Ca<jats:sup>2+<\/jats:sup>, acting through calmodulin at some specific step(s) distal to cAMP elevation and prior to pregnenolone formation, is involved in FPH\u2010induced progesterone accumulation, apparently with the participation of both extracellular and intracellular pools of Ca<jats:sup>2+<\/jats:sup>. In the oocyte, mobilization of Ca<jats:sup>2+<\/jats:sup> from intracellular stores appears to be of primary importance to maturation while extracellular Ca<jats:sup>2+<\/jats:sup> is not. These data provide further evidence that Ca<jats:sup>2+<\/jats:sup> mediates the hormonally provoked responses in both cell types in the intact follicle, but that the source of Ca<jats:sup>2+<\/jats:sup> may differ. Using intact follicles it seems apparent that exploiting this difference with selective inhibitors provides a means for differential modulation and functional uncoupling of these cells with regard to steroidogenesis and steroid action.<\/jats:p>","DOI":"10.1002\/jez.1402440116","type":"journal-article","created":{"date-parts":[[2005,6,11]],"date-time":"2005-06-11T12:56:00Z","timestamp":1118494560000},"page":"133-143","source":"Crossref","is-referenced-by-count":16,"title":["Sources of calcium and the involvement of calmodulin during steroidogenesis and oocyte maturation in follicles of <i>Rana pipiens<\/i>"],"prefix":"10.1002","volume":"244","author":[{"given":"Susan Kleis\u2010San","family":"Francisco","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Allen W.","family":"Schuetz","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2005,4,25]]},"reference":[{"key":"e_1_2_1_2_1","doi-asserted-by":"publisher","DOI":"10.1016\/0016-6480(86)90100-0"},{"key":"e_1_2_1_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/0016-6480(86)90035-3"},{"key":"e_1_2_1_4_1","doi-asserted-by":"publisher","DOI":"10.1095\/biolreprod33.1.79"},{"key":"e_1_2_1_5_1","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1975.sp011076"},{"key":"e_1_2_1_6_1","doi-asserted-by":"publisher","DOI":"10.1038\/312315a0"},{"key":"e_1_2_1_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/0002-9378(83)90496-9"},{"key":"e_1_2_1_8_1","doi-asserted-by":"publisher","DOI":"10.1016\/0012-1606(83)90248-8"},{"key":"e_1_2_1_9_1","doi-asserted-by":"crossref","first-page":"9404","DOI":"10.1016\/S0021-9258(19)70576-6","article-title":"Xenopus laevis oocyte calmodulin in the process of meiotic maturation","volume":"255","author":"Cartaud A.","year":"1980","journal-title":"J. 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