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- Liu, Y X, et al.
(författare)
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Gonadotropin regulation of tissue-type and urokinase-type plasminogen activators in rat granulosa and theca-interstitial cells during the periovulatory period.
- 1987
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Ingår i: Molecular and Cellular Endocrinology. - 0303-7207 .- 1872-8057. ; 54:2-3, s. 221-9
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Tidskriftsartikel (refereegranskat)abstract
- Plasminogen activators (PAs) are believed to be involved in ovulation. Because both tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) are secreted by cultured rat granulosa cells, we have examined the activities of these proteins in ovarian homogenates as well as granulosa and theca-interstitial (TI) cells during gonadotropin-induced ovulation. Immature rats were injected with 20 IU pregnant mare serum gonadotropin (PMSG) to initiate follicle development, followed by treatment with 10 IU hCG 48 h later to induce ovulation. Ovarian proteins were separated by SDS-PAGE and PA activity determined by fibrin overlay. The activity of tPA, but not uPA, was stimulated following PMSG treatment in ovarian homogenates. Subsequent hCG injection further increased the tPA activity in a time-dependent manner, reaching a maximum (12 h after hCG treatment) immediately prior to ovulation and declined thereafter. Similar preovulatory increases in tPA activity were detected in isolated granulosa cells. Although both tPA and uPA activities were increased in TI cells after PMSG administration, no further increases were detected after hCG treatment. To estimate enzyme secretion, ovarian cells obtained at various preovulatory periods were incubated for 24 h in vitro. The ability of granulosa cells to secrete tPA, but not uPA, increased following in vivo PMSG and hCG treatment in a time-dependent manner, reaching a maximum immediately prior to ovulation. During the preovulatory period, an abrupt increase in tPA secretion by TI cells was also detected. Using immunohistochemical staining for tPA, it was found that ovarian sections from preovulatory rats at 12 h after hCG injection stained positively in granulosa, theca interna, and interstitial gland cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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- Ny, Tor, et al.
(författare)
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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
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 262:24, s. 11790-3
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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