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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Spermatogenesis is dependent on stimulation by pituitary gonadotropins, FSH and LH. Targets for these hormones are Sertoli and Leydig cells, respectively. The effect of LH on spermatogenesis is mediated by testosterone. In addition to hormones, interactions between neighbouring cells seem to regulate spermatogenesis. This is reflected by cyclic secretion of several proteins by the seminiferous epithelium, of which plasminogen activator is a good example. While it is controlled by FSH a factor in preleptotene spermatocytes may also influence its cyclic secretion pattern. Both testosterone and FSH have a cyclic action in the seminiferous epithelium. The androgens seem to predominate in stages where spermiation, onset of meiosis and the highest rate of RNA transcription occur (VII-XI). FSH is most active in stages that contain meiotic divisions and early spermiogenesis (XIII-V), greatly stimulating the production of cyclic AMP. To investigate further the "second messengers" of FSH action in the seminiferous epithelium, the cellular distribution of calmodulin was analyzed using an indirect immunocytochemical method. In addition to their clear cyclic distribution in primary spermatocytes and in spermatids, Sertoli cells also showed a bright calmodulin immunofluorescence that was apparently cyclic. These observations suggest a local calmodulin and calcium regulation of spermatogenesis.
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PMID:Cell interactions in the rat seminiferous epithelium with special reference to the cellular distribution of calmodulin. 308 86

Plasminogen activators convert plasminogen into plasmin, a serine protease that initiates extracellular proteolysis. Two types of plasminogen activator activities have recently been demonstrated in granulosa cells, and the proteolysis-inducing enzymes are believed to be involved in ovulation. However, little attention has been paid to the presence of these enzymes in oocytes. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by a fibrin overlay technique, we studied plasminogen activator activity in oocytes. Denuded oocytes collected from ovaries of hypophysectomized, estrogen-treated immature rats contained a tissue-type plasminogen activator (tPA), but not urokinase (uPA). In contrast, oocyte-free granulosa cells in these preantral follicles contained uPA, but not tPA. The tPA activity found in oocytes was plasminogen-dependent; incubation with increasing numbers (25-200) of denuded oocytes resulted in a dose-dependent increase in fibrinolysis only in the presence of plasminogen. Cellular localization of tPA was studied in the preantral follicles using an immuno-cytochemical method. Positive tPA staining was detected in the cytoplasm, but not in the germinal vesicle or zona pellucida of the oocytes. Furthermore, analysis using a reverse fibrin-overlay method did not reveal the presence of a plasminogen activator inhibitor. Culturing of denuded oocytes for 24 h increased the cellular content of tPA, but the enzyme activity was not further enhanced by treatment with FSH or forskolin. Also, no tPA activity was detected in the medium. We further studied plasminogen activator activities in the cumulus-oocyte complexes. Although only tPA activity was detected in freshly obtained cumulus-oocyte complexes, incubation for 24 h increased both tPA and uPA activity. Furthermore, tPA, but not uPA, activity was stimulated by treatment with FSH or forskolin. This was accompanied by the secretion of tPA into the medium. The identity of tPA and uPA in the cumulus-oocyte complexes was further confirmed by immunoprecipitation with specific antibodies. Isolation of denuded oocytes and cumulus cells after hormonal stimulation of the cumulus-oocyte complexes suggested that tPA activity was stimulated in both cell types and that the cumulus cells may mediate the action of FSH and forskolin on oocytes. In conclusion, the detection and regulation of tPA activity in cumulus-oocyte complexes suggest possible involvement of this enzyme in ovulation or the process of cumulus cell expansion and dispersion. Changes in oocyte tPA content may also serve as an indicator of oocyte development.
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PMID:Identification and regulation of tissue plasminogen activator activity in rat cumulus-oocyte complexes. 309 95

We have previously shown that FSH caused a dose-dependent increase in plasminogen activator (PA) production by cultured rat granulosa cells. PA production was assayed by culturing granulosa cells, obtained from immature diethylstilbestrol-treated rats, on [125I]fibrin plates and determining the extent of fibrinolysis after the addition of the specific substrate plasminogen. To study the effect of ovarian steroids on FSH-stimulated PA production, concomitant treatment with FSH and estradiol [(E2) 10(-7) M], progesterone [(P) 10(-6) M], testosterone [(T) 10(-7) M] or 5 alpha-dihydrotestosterone [(DHT) 10(-7) M] were tested in these cultures. Treatment with E2 significantly enhanced the FSH-stimulated PA production by 35-210% over the whole range of the FSH dose response curve. The augmentation of FSH-stimulated PA production by E2 was not affected by the concomitant treatment with the antiprogestin RU 486 (10(-6) M). Similarly, P significantly enhanced the FSH-stimulated PA production by 34 to 90%. The stimulating action of P on FSH-dependent PA production was blocked by the simultaneous treatment with RU 486. Concomitant treatment with T significantly increased the FSH-induced PA production by 22-60%. That the effect of T was not due to the aromatization to E2 was evidenced by the augmentation by DHT of FSH-stimulated PA production. DHT caused a significant 20-39% enhancement in the responsiveness of the granulosa cells to FSH by further increasing PA production. The enhancement of PA production by androgen is decreased partially by concomitant treatment with the antiandrogen flutamide (10(-5) M) and the antiprogestin RU 486. These in vitro data demonstrated the importance of estrogens, progestogens, and androgens in modulating the stimulating effect of FSH on PA production by immature rat granulosa cells.
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PMID:Estrogens, progestogens, and androgens enhance the follicle-stimulating hormone-stimulated plasminogen activator production by cultured rat granulosa cells. 310 15

Granulosa cells from immature rats primed with diethylstilbestrol (DES) showed a fivefold rise in the activity of secreted plasminogen activator (PA) in response to human FSH. The dose giving 50% of the maximum response (ED50) was 10 ng/ml. Glucocorticoid hormones significantly suppressed PA activity in both control cells and cells stimulated with FSH (ED50 = 50 nmol dexamethasone/l; 1 mumol corticosterone/l). Cortexolone (2.5 mumol/l) significantly ameliorated this suppression, indicating that the response to glucocorticoids is receptor-mediated. These data, together with the time delay required for glucocorticoids to take effect (5 h), suggest that glucocorticoids induce the production of a specific PA inhibitor in granulosa cells.
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PMID:Modulation of plasminogen activation by glucocorticoid hormones in the rat granulosa cell. 311 39

Two molecular variants of plasminogen activator (PA): urokinase (uPA) and tissue-type plasminogen activator (tPA), have been reported to be synthesized in the rat testis. Data obtained in this study using monospecific antibodies raised against uPA and tPA in immunoblotting and bioimmunoassay protocols consistently demonstrate that only tPA (and not uPA) is synthesized by bovine Sertoli cell-enriched cultures, and is induced by bovine FSH. Zymographic analysis of conditioned medium on gels containing plasminogen and casein showed a dominant PA proteolytic band (72 kDa) which co-migrated with human tPA. A proteolytic band (43 kDa), which was also secreted by FSH-stimulated cells, was not present when protection was afforded from auto-proteolysis by aprotinin, and was therefore concluded to be a proteolytic fragment of tPA, and not uPA.
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PMID:Only tissue-type plasminogen activator is secreted by immature bovine Sertoli cell-enriched cultures. 312 22

FSH and GnRH both stimulate rat granulosa cells to produce tissue-type plasminogen activator (tPA). We have studied the molecular mechanisms involved in the action of these hormones by measuring tPA mRNA levels in primary cultures of rat granulosa cells. When granulosa cells were cultured in the presence of FSH or GnRH the level of tPA mRNA was increased 20- and 12-fold, respectively. The induction of tPA mRNA by FSH and GnRH was additive and the kinetics of induction differed. The effect of FSH could be mimicked by bromo-cAMP or forskolin, and was drastically enhanced by cotreatment with the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine. These findings are consistent with the notion that FSH mediates its effect through the protein kinase A pathway. GnRH is believed to augment phospholipid turnover in granulosa cells, leading to the activation of the protein kinase C pathway. Like GnRH, the protein kinase C activator phorbol myristate acetate also induced tPA mRNA in granulosa cells. In the presence of the protein synthesis inhibitor, cycloheximide, FSH-stimulated tPA message levels were enhanced by 30-fold, revealing superinduction of tPA mRNA levels by this pathway. In contrast the induction of tPA mRNA by GnRH was inhibited by cycloheximide indicating that the synthesis of an intermediate protein is required for the GnRH effect. Our data suggest that FSH and GnRH increase the tPA mRNA levels by two distinct pathways in cultured granulosa cells, providing a model system for studying the hormonal regulation of tPA gene expression.
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PMID:Hormonal regulation of tissue-type plasminogen activator messenger ribonucleic acid levels in rat granulosa cells: mechanisms of induction by follicle-stimulating hormone and gonadotropin releasing hormone. 313 93

As stated earlier, the mammalian ovary maintains the continuous development of follicles, but only a few are selected to ovulate and form corpora lutea. These processes are regulated primarily by the gonadotropins and involve specific, sequential changes in the function of theca cells and granulosa cells. Data from recent studies (summarized in Figure 3) show that specific genes are turned on or off at different stages of follicular growth in response to estradiol and different amounts of gonadotropins and cAMP. For example, mRNA for RII51 in granulosa cells and theca cells increases in association with small increased in cAMP but is markedly reduced by the LH surge and high cAMP. The content of mRNA for other kinase subunits, RI and C alpha, show little or no change during similar hormonal changes. In theca cells, mRNA for 17 alpha-hydroxylase increased and decreased in a manner similar to that for RII51. In contrast, levels of mRNA for P450scc increased only gradually in follicles but were markedly increased by the LH surge and high concentrations of cAMP and then appeared to be constitutively expressed in rat corpora lutea in a cAMP-independent manner. PGS and t-PA appear to follow yet another pattern: rapid induction by the LH surge followed by a rapid decline in association with ovulation. One major task for reproductive endocrinologists and molecular biologists now is to determine how low and high concentrations of cAMP act to turn on and turn off the expression of these specific genes at specific times during follicular maturation. A working model of the molecular events occurring in theca and granulosa cells of PO follicles is shown in Figure 4. LH acts on theca cells via cAMP ro regulate both P450scc and P450(17) alpha mRNA levels, leading to increased biosynthesis of androstenedione. The mechanisms by which cAMP acts in theca cells remain to be determined but appear to involve an increase in the content of RII51, P450scc, and P450(17) alpha. In granulosa cells, androstenedione is converted to estradiol by the aromatase P450 enzyme system. Estradiol, in turn, binds to estradiol receptors present in these cells and may thereby regulate gene expression. However, despite the presence of estradiol and estradiol receptors, little or no effect of estradiol is observed unless FSH acts via the FSH receptor to increase intracellular concentrations of cAMP. In a manner not yet understood, cAMP appears to enhance the actions of estradiol.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Molecular aspects of hormone action in ovarian follicular development, ovulation, and luteinization. 328

Production of plasminogen activator (PA) by granulosa cells (GC) and its stimulation by gonadotropins led to the suggestion that PA is involved in ovulation. However, whereas only LH may be regarded as the ovulation-inducing hormone in the rat, FSH was found to be much more potent than LH in enhancing PA production by GC. Assuming that the entire follicular wall, rather than isolated GC, is involved in follicular rupture, we have examined activity of PA in intact follicles. LH (NIH-LH-S23) was 5-fold more potent than FSH (NIH-FSH-S14), and purified ovine LH and FSH were equally potent in enhancing follicular PA activity. Furthermore, injection into the ovarian bursa of proestrous rats of epsilon-amino-caproic acid and benzamidine (0.05-0.25 mmol), inhibitors of serine proteases, including PA and plasmin, resulted in a dose-dependent inhibition of ovulation without causing changes discernible by histological examinations of the ovaries. Whereas steroids did not change basal follicular PA production in culture, addition of estradiol-17 beta [(E2) 1 microgram/ml] but not progesterone or testosterone, further enhanced LH-stimulated PA. Aminoglutethimide phosphate (10(-3) M) and 17 beta-formamidoandrost-4-en-3-one inhibited LH-induced increase in follicular PA and this inhibition was reversed by addition of E2. Intrabursal injection of indomethacin, an inhibitor of cyclooxygenase, and of nordihydroguaiaretic acid, an inhibitor of lipoxygenase pathway of arachidonic acid metabolism at doses which effectively blocked ovulation (0.3 mg/bursa) had no effect on PA content of the follicles. Likewise, indomethacin (10 microM) and nordihydroguaiaretic acid (100 microM) did not affect LH-stimulated PA in vitro. In conclusion, LH, the physiological trigger of ovulation is, at least, as potent as FSH in stimulating follicular PA activity. The role of serine proteases, most probably of PA and plasmin, in ovulation is further corroborated by a pharmacological approach. LH stimulation of follicular PA appears to be enhanced by E2 but is not mediated by arachidonic acid metabolites.
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PMID:Follicular plasminogen activator: involvement in ovulation. 391 2

The FSH activity in equine (e) FSH, eLH, eCG, and ovine LH were examined and compared to that in the standard reference preparation NIH FSH-S13 by three types of assay: the FSH radioreceptor assay with rat testicular homogenate and the stimulation of plasminogen activator production and steroidogenic activity in granulosa cells from diethylstilbestrol (DES)- or eCG-primed donor rats. The difference in the two types of granulosa cells was that the eCG-primed cells have already acquired significant aromatase activity. With the exception of oLH, which showed very little FSH activity (approximately 0.03-0.08 X NIH FSH-S13) throughout the three assays, the equine gonadotropins exhibited great variations in activity with respect to each assay. eFSH, the most active molecule in these assays, had an activity of 44 X NIH FSH-S13 in the receptor binding assay, 8.75 X NIH FSH-S13 in plasminogen activator production, and 4-5 X NIH FSH-S13 in steroid production when assayed in the DES-primed granulosa cells. In the eCG-primed cells, eFSH showed an activity of 4.2 X NIH FSH-S13 in plasminogen activator production and 8.2 X NIH FSH-S13 in progesterone production. eLH had an activity of 10 X NIH FSH-S13 in FSH radioreceptor assay, but showed very little activity and behaved like oLH in stimulation of the cellular responses of DES-primed granulosa cells. However, when eLH was assayed in the eCG-primed cells, it did show stimulating activity with respect to the production of plasminogen activator and progesterone; however, the dose-response curves were not parallel to those of eFSH and eCG. eCG had much less FSH receptor-binding activity (0.29 X NIH FSH-S13) than eLH. It behaved like a LH molecule in DES-primed granulosa cells, but did show activity (approximately 1 X NIH FSH-S13) in stimulating the production of plasminogen activator and progesterone in eCG-primed granulosa cells. From these results, we conclude that under our culture conditions, neither eLH nor eCG was active in the DES-primed granulosa cells, but both were active in the eCG-primed cells, and that the choice of assay conditions and reference standards is very important. Different types of assay may give rise to completely different comparisons for the same molecules. The equine gonadotropins provide a particularly dramatic example of such differences.
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PMID:Priming procedure and hormone preparations influence rat granulosa cell response. 391 55

Although treatment of cultured granulosa cells with gonadotropins increases their fibrinolytic activity, the biochemical nature of this effect is unclear. We have used sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fibrin autography techniques to characterize the fibrinolytic components secreted by granulosa cells. The fibrinolytic activity of these cells results from the production of both a tissue-type plasminogen activator (t-PA) and a urokinase-like activator (u-PA). The cells also produce an inhibitor of fibrinolysis (antiactivator). FSH and LH stimulate t-PA activity and suppress antiactivator activity, while u-PA activity is not affected by the gonadotropins. The differential regulation of these molecules by the gonadotropins may be essential for ovulation.
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PMID:Cultured granulosa cells produce two plasminogen activators and an antiactivator, each regulated differently by gonadotropins. 391 58


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