Regulation of tissue-type plasminogen activator activity and messenger RNA levels by gonadotropin-releasing hormone in cultured rat granulosa cells and cumulus-oocyte complexes.
1987 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 262, no 24, 11790-3 p.Article in journal (Refereed) Published
Gonadotropin-releasing hormone (GnRH) acts directly on the ovary to induce ovulation in hypophysectomized proestrous rats. Because plasminogen activators (PAs) are implicated in gonadotropin-induced ovulation, we have studied the effect of GnRH on ovarian PA synthesis. GnRH induced tissue-type PA (tPA) secretion by cultured rat granulosa cells, but inhibited the secretion of urokinase-type PA. These effects were blocked by co-treatment with a GnRH antagonist, suggesting that stereospecific GnRH receptors are involved. Follicle-stimulating hormone (FSH) also induced tPA in granulosa cells but with a different time course than GnRH; the combined effect of FSH and GnRH was additive. The GnRH effect was mimicked by the calcium- and phospholipid-dependent protein kinase C activator, phorbol myristate acetate. In isolated cumulus-oocyte complexes and cumulus cells, GnRH treatment also increased tPA activity. In contrast, treatment of denuded oocytes with GnRH did not increase enzyme activity. After GnRH stimulation of the cumulus-oocyte complexes, tPA content in the denuded oocyte was elevated, suggesting that the cumulus cells mediate the action of GnRH to increase the oocyte enzyme levels. Hybridization experiments using a labeled rat tPA-specific DNA probe showed that both FSH and GnRH increased the level of tPA mRNA in cultured granulosa cells; the stimulatory effect of GnRH was blocked by the GnRH antagonist. Our results indicate that GnRH treatment increases tPA secretion by cultured granulosa cells and cumulus-oocyte complexes. The stimulation of enzyme activity in the granulosa cells is accompanied by increases in tPA mRNA levels.
Place, publisher, year, edition, pages
1987. Vol. 262, no 24, 11790-3 p.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:umu:diva-59879PubMedID: 3114254OAI: oai:DiVA.org:umu-59879DiVA: diva2:556977