Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.1 (phosphodiesterase)
18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regulation by FSH (follitropin; follicle-stimulating hormone) of FSH receptor mRNA and protein (FSH binding) was studied using cultured Sertoli cells isolated from 21-day-old rats. FSH induced a dose-dependent and almost complete down-regulation of receptor mRNA at 4 h after addition of the hormone. At subsequent time points (16 h and later) the FSH receptor mRNA levels had returned close to control values. The effect of FSH was mimicked by dibutyryl cyclic AMP (dbcAMP) and forskolin, and the phosphodiesterase inhibitor methyl-isobutylxanthine (MIX) prolonged the FSH action. These findings indicate that the effect of FSH on its receptor mRNA was mediated by cAMP. A down-regulatory effect of FSH and dbcAMP on FSH receptor mRNA was also observed in the presence of the protein synthesis inhibitor cycloheximide, suggesting a direct effect of FSH/dbcAMP on the expression of the FSH receptor gene. Transcriptional run-on experiments revealed that FSH did not inhibit initiation of the FSH receptor gene; hence a post-transcriptional mechanism is involved. Binding of 125I-FSH to the cultured Sertoli cells was rapidly (4 h) decreased when the cells were incubated with FSH or FSH in combination with MIX. This effect can be explained by ligand-induced receptor sequestration. In contrast, incubation of Sertoli cells with dbcAMP had no effect on binding of 125I-FSH after 4 h, but resulted in a 60% loss of FSH binding sites after 24 h, probably caused by decreased mRNA expression. In conclusion, FSH receptor down-regulation in Sertoli cells is effected not only by the well-documented ligand-induced loss of receptors from the plasma membrane, but also involves a cAMP-mediated decrease of FSH receptor mRNA through a post-transcriptional mechanism.
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PMID:Follitropin receptor down-regulation involves a cAMP-dependent post-transcriptional decrease of receptor mRNA expression. 172 86

Responsiveness of the Sertoli cell after FSH pretreatment was evaluated in terms of androgen aromatization. Sertoli cell cultures were preincubated with FSH for 24 h, then cells were washed free of hormone and reincubated with FSH in the presence of androstendione. The estrogen accumulated in the medium was measured by RIA. Gonadotropin pretreatment produced a marked refractory state, and a second challenge with FSH did not produce an increase in androgen aromatization. A dose-response study showed that FSH pretreatment produced three separate effects on Sertoli cell steroidogenesis: an increased basal production of estrogen; a decreased maximal response when doses of 10 ng/ml FSH or higher were employed in the preincubation; and a decreased sensitivity of the Sertoli cell to FSH. In the last case, the ED50 was reduced approximately 3- to 5-fold. Such an impaired stimulation of androgen aromatization was no longer present when cells were incubated with the phosphodiesterase inhibitors methyl-isobutyl-xanthine (MIX). In the presence of this inhibitor, refractory cells responded to FSH better than the control cells. The possibility that MIX stimulated cAMP accumulation by acting as antagonist of purine receptor was ruled out by the finding that the nonxanthine phosphodiesterase inhibitor 4-(3-butoxy-4-methoxybenzyl)2-imidazolidinone (Ro 20-1724) also reverted the refractory state. Pretreatment of the Sertoli cells with FSH produced an impaired response in the second incubation also to isoproterenol, cholera toxin, and forskolin. The response to these compounds was apparently normal when cells were incubated in the presence of MIX or Ro 20-1724. Conversely, refractory cells responded to (Bu)2cAMP in a manner indistinguishable from the fully responsive control cells. These data demonstrate that FSH induces homologous and heterologous refractory states of the Sertoli cell reflected by an impaired estrogen production. The finding that phosphodiesterase inhibitors fully restore the FSH response suggests an important role of phosphodiesterase in the induction and/or maintenance of such refractoriness.
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PMID:Effect of phosphodiesterase inhibitors on Sertoli cell refractoriness: reversal of the impaired androgen aromatization. 241 18

Proopiomelanocortin and its derivative peptides alpha MSH and beta-endorphin are produced by Leydig cells. beta-Endorphin or another testicular opiate is believed to suppress Sertoli cell hypertrophy. The goal of this study was to determine the effects of another proopiomelanocortin-derived peptide on Sertoli cells. The activities of both alpha MSH and des-acetyl alpha MSH have been compared, since this latter peptide has been identified in testicular extracts. Both alpha MSH and des-acetyl alpha MSH stimulated cAMP accumulation in the media of primary Sertoli cell cultures when incubated in the presence of a phosphodiesterase inhibitor, FSH or forskolin. Both peptides shifted the FSH dose-response curve to the left, making the cells more sensitive to this gonadotropin. The apparent potencies of alpha MSH and its des-acetyl derivative, as measured in Sertoli cells, were similar. We conclude that the MSHs are one of a group of modulators regulating Sertoli cells via the cAMP system, and Sertoli cells are equally responsive to alpha MSH and des-acetyl alpha MSH, unlike central nervous system and melanocytes which show differential responses to these peptides.
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PMID:Stimulation of adenosine 3',5'-monophosphate production in rat Sertoli cells by alpha-melanotropin-stimulating hormone (alpha MSH) and des-acetyl alpha MSH. 241 22

Stimulation of rat granulosa cell aromatase activity by FSH has recently been used as a sensitive biological end point to develop an in vitro FSH bioassay. The present report provides a detailed validation and application of this assay. In the presence of androstenedione and diethylstilbestrol, FSH stimulated estrogen production in a dose-dependent manner. Although addition of high doses of a phosphodiesterase inhibitor [1-methyl-3-isobutyl xanthine (MIX)] decreased maximal estrogen production, treatment with 0.125 mM MIX increased the sensitivity of granulosa cells to FSH, presumably by minimizing endogenous cAMP breakdown. Addition of insulin and human CG (hCG) further synergistically enhanced granulosa cell sensitivity to FSH. Although inclusion of gonadotropin-free serum obtained from hypophysectomized male rats decreased the assay sensitivity, pretreatment of serum with polyethylene glycol [(PEG) 10-14%] resulted in a dose-dependent decrease in the serum-interfering effect. Studies using exogenous [125I]iodo-rat FSH or RIA measurement indicated recovery of 94-98% FSH after pretreatment of serum with 12% PEG. In the presence of the PEG-pretreated gonadotropin-free serum (4%), ovine, rat, and human FSH preparations induced parallel dose-response curves for estrogen production with minimal detectable doses of 0.12 ng, 0.12 ng, and 0.12 mIU/culture, respectively. In contrast, treatment with GH, PRL, TSH, and ACTH did not affect estrogen production. The apparent stimulatory effect of high doses (greater than 60 ng/culture) of LH and hCG could be attributed to FSH contamination or intrinsic FSH activity in these preparations. Changes in serum bioactive FSH levels were studied in adult male rats after GnRH administration. GnRH (5 micrograms/rat) treatment significantly elevated FSH levels within 30 min after injection. Maximal increases (approximately 2.8-fold) in serum bioactive FSH were observed between 60-120 min. At 8 h after treatment, FSH levels decreased to control levels. Comparison between granulosa cell aromatase bioassay and RIA results indicated no apparent changes in the bio- to immuno- ratio of FSH after GnRH treatment. In conclusion, extreme sensitivity of the bioassay allows the measurement of circulating levels of bioactive FSH. Since rat granulosa cells respond to FSH preparations from different species, the in vitro assay should also provide valuable information on FSH levels in many animal species including those lacking a specific RIA. Measurement of serum levels of bioactive FSH should provide insight regarding the role of FSH in various physiological and pathological conditions.
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PMID:Granulosa cell aromatase bioassay for follicle-stimulating hormone: validation and application of the method. 242

Previous studies have established the ovarian granulosa cell as a site of insulin-like growth factor-I (IGF-I) secretion and action, suggesting an autocrine function for this peptide in the ovary. To better understand how this putative autocrine system is regulated and its interface with the classic ovarian trophic hormones FSH, LH, and estradiol (E2), we have studied the effects of these hormones on the secretion of immunoreactive IGF-I (iIGF-I) by cultured porcine granulosa cells. Immature granulosa cells were cultured under serum-free conditions which were optimized to allow maximal iIGF-I production and hormonal responsivity. Measurements of iIGF-I were made after minimizing the influence of IGF-binding proteins by either acid gel filtration or reverse phase chromatography. Since the two preparative procedures gave roughly comparable results, the more expeditious reverse phase procedure was chosen for most samples. Cycloheximide virtually eliminated measurable iIGF-I in culture, suggesting that the peptide measured was newly synthesized, and degradation of IGF-I by cultured granulosa cells was negligible. Consequently, the medium levels provided an accurate indication of cellular secretion over the collection period. Under optimal culture conditions, iIGF-I was readily measurable and responsive to treatment with ovarian trophic hormones. The iIGF-I levels in several experiments with these hormones were as follows: FSH treatment, 1.58 +/- 0.21 times the control value (n = 5 experiments); E2 treatment, 1.26 +/- 0.12 times the control value (n = 5); E2 plus FSH, 3.12 X 0.31 times the control value (n = 8); LH, 1.33 +/- 0.12 times the control value (n = 3); LH plus FSH, 1.78 +/- 0.2 times the control value (n = 1). To assess the role of cAMP in the mediation of gonadotropin effects in this system, granulosa cells were treated with a phosphodiesterase inhibitor (methylisobutylxanthine), which resulted in iIGF-I levels 1.61 +/- 0.7 times the control level. In the presence of FSH, a further stimulatory effect was demonstrated (3.76 +/- 0.29 times control). In addition, the cAMP analog 8-bromo-cAMP dramatically increased iIGF-I levels (6.3 +/- 0.72 times control). These data provide the first demonstration that gonadal iIGF-I secretion can be stimulated by the principal hormones involved in trophic regulation of the ovary. As with other gonadotropin-dependent functions of granulosa cells, this effect appears to be mediated by cAMP and enhanced by E2. This interface between circulating hormones and autocrine systems could provide an important mechanism to amplify the effects of gonadotropic hormones on a local level.
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PMID:Gonadotropins and estradiol stimulate immunoreactive insulin-like growth factor-I production by porcine granulosa cells in vitro. 243 Jul 86

Animals with impaired immune function show numerous reproductive disorders. To determine whether immune factors might play a direct role in the regulation of ovarian function, we examined the effects of Concanavalin-A-stimulated lymphocyte supernates (CAS) on steroidogenesis by cultured rat granulosa cells. Granulosa cells from immature estrogen-primed rats were incubated for 48 h with increasing doses of CAS in the presence or absence of FSH. In the absence of FSH, CAS produced a dose-dependent increase in progestin (progesterone and 20 alpha-hydroxyprogesterone) production to a maximum of 190-fold greater than untreated controls, but did not stimulate estrogen production. In the presence of FSH, the stimulatory effect of CAS on progestin production was additive with that of FSH. In contrast, CAS inhibited FSH-stimulated estrogen production in a dose-dependent manner. The maximum inhibition was greater than 90%. Addition of the phosphodiesterase inhibitor isobutylmethylxanthine to CAS-containing cultures significantly enhanced the stimulatory effect of CAS on progesterone production, suggesting that this action may be exerted through a cAMP-mediated pathway. The stimulatory component of CAS was heat labile, acid stable, and required a trypsin-sensitive cell surface recognition site, whereas the inhibitory component was both heat and acid stable. Neither the stimulatory nor the inhibitory actions of CAS were mimicked by treating granulosa cells with supernates from Concanavalin-A-stimulated neonatal cardiac or hepatic cell cultures. Thus, the present studies demonstrate that secretory products of lymphocytes (collectively termed lymphokines) can affect steroidogenesis in cultured rat granulosa cells. These data imply that immune cell factors may play a significant role in the differentiation and maturation of granulosa cells.
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PMID:Lymphokines from concanavalin-A-stimulated lymphocytes regulate rat granulosa cell steroidogenesis in vitro. 245 14

To characterize the transcriptional effects of human (h)FSH and hCG on the POMC gene, primary rat granulosa cells were transiently transfected with a chloramphenicol acetyltransferase (CAT) reporter plasmid under the control of the POMC promoter and 5' region. POMC-CAT contains a fragment of the rat POMC gene, extending from nucleotide -704 to nucleotide +63, fused to the CAT gene. Treatment of POMC-CAT-transfected cells with either hFSH (20 ng/ml) or hCG (10 ng/ml) significantly increased CAT enzyme activity; however, neither hCG nor hFSH increased CAT enzyme activity in cells transfected with pSV2-CAT, a reporter plasmid under the control of the SV40 virus promoter and 5' region. The phosphodiesterase inhibitor isobutylmethylxanthine or the nonhydrolyzable cAMP analog cAMP-chlorothiophenyl significantly increased CAT activity in POMC-CAT-transfected granulosa cells. Human FSH stimulated transcription 10, 20, and 40 h after treatment, but FSH stimulation at the two earlier time points was 2.5- to 5.5-fold greater than that at 40 h. Gonadotropin-stimulated steroidogenesis was equivalent in POMC-CAT-transfected granulosa cells, untransfected, and mock-transfected cells. This indicates that transfection left the physiological hormone response intact. These data demonstrate the following. 1) 767 basepairs of the rat POMC gene are enough to confer gonadotropin stimulation on the CAT marker gene in granulosa cells. 2) Although the POMC promotor lacks a well conserved cAMP response element, either of two different pharmacological manipulations of granulosa cells that raise intracellular cAMP can also stimulate POMC-driven CAT expression. 3) Transfected primary cultures of granulosa cells provide a nontransformed, physiologically relevant model with which to study hormone-regulated gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Gonadotropin regulation of the rat proopiomelanocortin promoter: characterization by transfection of primary ovarian granulosa cells. 246 53

Although factors that regulate cAMP and steroid production in granulosa cells of hen preovulatory follicles have been well studied, much less is known of the mechanisms that control steroidogenesis in the adjacent thecal layer. These studies were conducted to examine the involvement and interaction of cAMP and protein kinase-C in modulating androstenedione output from isolated ovarian thecal cells collected from the second largest preovulatory follicle. Treatment of thecal cells with ovine LH (0.01-100 ng/tube) caused a dose-dependent increase in androstenedione secretion. Although coincubation of cells with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (0.1 mM) potentiated the effects of LH on steroid production, cAMP levels increased only in response to the higher doses of LH (10-100 ng/tube). Small but significant increases in cAMP accumulation and androstenedione production were observed in response to vasoactive intestinal peptide (0.1 and 1.0 microM), but not to 100 ng/tube chicken FSH, in the presence of 0.1 mM 3-isobutyl-1-methylxanthine. Treatment of thecal cells with cholera toxin (0.001-100 ng/tube) or forskolin (0.001-10 microM) resulted in a dose-dependent increase in cellular cAMP levels and androstenedione secretion. Thecal cell androstenedione production was also stimulated by the cAMP analog 8-bromo-cAMP (0.1-1.0 mM). Incubation of thecal cells with phorbol 12-myristate 13-acetate (PMA; 0.32-162 nM) or 1-oleoyl-2-acetylglycerol (OAG; 2.5-126 microM) increased basal steroidogenesis (progesterone and androstenedione production) in the absence of a rise in cAMP levels. By contrast, the stimulatory effects of 1 ng/tube LH on androstenedione, but not progesterone, production were attenuated by the presence of PMA (3.2-162 nM) or OAG (25-126 microM). Only a high concentration of OAG (126 microM) suppressed cAMP accumulation stimulated by LH (50 ng/tube). Phorbol ester treatment (32-162 nM PMA) also inhibited androstenedione production in thecal cells stimulated by the presence of 8-bromo-cAMP (1 mM), indicating a post-cAMP effect of protein kinase-C activity on steroidogenesis. In contrast to the effects of PMA, phorbol 13-monoacetate (162 nM), a nontumor-promoting analog of PMA which does not activate protein kinase-C, did not alter basal steroidogenesis, nor did it affect androstenedione secretion stimulated by LH or 8-bromo-cAMP. Data from the present studies indicate that the adenylyl cyclase-cAMP pathway can mediate the induction of thecal cell steroidogenesis by extracellular signals (i.e. LH and vasoactive intestinal peptide), whereas activated protein kinase-C can both stimulate and inhibit androstenedione production, depending upon the hormonal environment.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Regulation of androstenedione production by adenosine 3',5'-monophosphate and phorbol myristate acetate in ovarian thecal cells of the domestic hen. 247 40

Immature Sertoli cells of the testicular seminiferous tubule maintain the expression of their differentiated phenotype when cultured in unsupplemented medium. In preliminary experiments we observed that foetal bovine serum (FBS) stimulates polyphosphoinositides (PI) hydrolysis in Sertoli cells. We then evaluated the effect of serum on the function of the immature Sertoli cell in culture, in terms of cAMP and estrogen production. Treatment of Sertoli cells for 30 min with 1-10% FBS had no effect on basal cAMP accumulation but abolished the response to FSH. The serum concentration producing half-maximal inhibition of the FSH-dependent cAMP accumulation was 0.5-1%. Comparison of the FSH-dose-response in the absence or presence of serum showed a decreased maximal response when serum was present. Sertoli cells exposed to serum were also less responsive to the beta-adrenergic agonist isoproterenol, to cholera toxin, and to forskolin. The serum inhibition was rapidly reversed upon removal of serum or incubating the cells with the phosphodiesterase inhibitor MIX (methyl-isobutyl-xanthine). Similarly to what observed with cAMP, serum affected androgen aromatization stimulated by FSH, isoproterenol, cholera toxin, forskolin and dibutyryl cAMP. These data indicate that factors present in serum can act as modulators of the Sertoli cell function in vitro by rapidly and reversibly inhibiting the cAMP and steroidogenic response of the Sertoli cell to FSH.
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PMID:Signal transduction in the Sertoli cell: serum modulation of the response to FSH. 253 47

Granulosa cells from ovarian follicles (greater than or equal to 1 mm diameter) in Booroola ewes which are homozygous (FF) or heterozygous (F+) for the F gene have previously been shown to produce significantly more cAMP in response to FSH or LH than those from similar sized follicles in ewes without the F gene (++). The aim of these studies was to test whether these F gene-specific differences arose because of differences in cAMP-phosphodiesterase (cAMP-PDE) activity. In the first study using 1 mumol cAMP/l as substrate, no F gene-specific effects were noted in cAMP-PDE activity in granulosa cells from small (1-2.5 mm diameter, n = 4 per genotype) or large (greater than or equal to 3 mm diameter, n = 4 per genotype) follicles from FF, F+ or ++ ewes, despite F gene-specific effects in FSH (1 microgram/ml)- and LH (0.1 microgram/ml)-induced cAMP accumulation in these same cell preparations. The overall mean levels of cAMP-PDE across all genotypes in cells from small and large follicles were 0.47 +/- 0.04 (S.E.M., n = 12) and 0.28 +/- 0.03 pmol cAMP/10(6) cells per min respectively; the mean PDE activity in cells from small follicles was significantly (P less than 0.05) higher compared with that in cells from large follicles. In a second study, granulosa cells from each genotype were pooled over all follicle sizes (greater than or equal to 1 mm diameter, one pool per genotype) and the rates of cAMP hydrolysis tested over a range of substrate concentrations (0-16 mumol/l) but no gene-specific differences with respect to the Michaelis constant and maximum velocity were noted.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Adenosine 3',5-cyclic monophosphate phosphodiesterase activity in granulosa cells from Booroola x Romney ewes with and without the F gene. 253 35


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