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Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Delta5-3beta HSDH activity has been assayed either by spectrophotometric method or by use of radioactive substrates. The enzymatic activity is equally distributed between mitochondrial and microsomal fractions verified by electronic microscopy. The specific activity is comparable in both fractions, as well as the optimal pH and the Km for NAD and for the substrates. The delta5-3beta Hut optimal pH, specific activity and sensitivity to the inhibitory action of various steroids are different when C19 and C21 steroids are used as substrates. Estrogens and cyclic AMP have also an inhibitory action on the oxidation of C21 steroids. Treatment of microsomal or mitochondrial membranes with phospholipase A releases fatty acids (mainly arachidonic) and decreases the enzymatic activity. "Adsorbtion" of the fatty acids on bovine serum albumin partially reactivates the delta5-3beta HSDH.
Steroids 1975 Nov
PMID:Human placental delta5-3beta hydroxysteroid dehydrogenase activity (delta5-3beta HSDH): intracellular distribution, kinetic properties, retroinhibition and influence of membrane delipidation. 0 79

Adrenals obtained from human abortices at midpregnancy were kept under conditions of tissue culture and the production of cortisol and dehydroepiandrosterone sulfate (3beta-hydroxy-5-androsten-17-one, 3-sulfate; DHA-S) monitored by radioimmunoassays for up to 2 weeks. Basal production of dehydroepiandrosterone sulfate was considerably higher than that of cortisol. alpha1-24corticotrophin, alpha1-39corticotrophin, (a long acting porcine corticotrophin) at the concentration of 1 mU/ml of culture medium in both instances, and dibutyryl cyclic AMP (1mM) enhanced the production of both steroids some 3 to 30 times above control values. Medium harvested from homologous pituitary cultures had comparable corticotrophic activity. It is concluded that at midpregnancy the regulation of corticoidogenesis implies the existence of a corticotrophic factor either identical or closely related to ACTH.
Steroids 1977 Mar
PMID:Exploration of the human fetal pituitary adrenal axis: stimulation of cortisol and dehydroepiandrosterone sulfate biosynthesis by homologous pituitary in organ culture. 14 Apr 79

The luteal cells obtained from bovine corpus luteum by enzymatic treatment have been maintained in tissue culture. When the cells were maintained in the absence of luteinizing hormone or dibutyryl cyclic AMP, they grew parallel to one another and were elongated, thus giving to the culture a fibroblastic appearance. No contact inhibition was observed and the progestin secretion rate was low (3 pg per cell per day). In contrast, when luteinizing hormone or dibutyryl cyclic AMP was present, the cells became polygonal, growing as a monolayer and taking the appearance of epithelial cells. In this case contact inhibition was observed. The rate of progestin secretion was 250 pg per cell per day. As soon as luteinizing hormone or dibutyryl cyclic AMP was removed from the media, the cells reverted to a fibroblastic appearance. Agents such as colcemid, vinblastin or cytochalasin B inhibited the morphological effect of luteinizing hormone or dibutyryl cyclic AMP. Since those agents are known to inhibit the assembly of microtubules, the data suggest that LH and dibutyryl cyclic AMP act by promoting the organization of microtubules from protein monomers. This microtubular system (cytoskeleton) is responsible for the morphological appearance of the cells. Concomitant with the morphological changes induced by luteinizing hormone and dibutyryl cyclic AMP an inhibition in the growth rate of luteal cells was observed. It suggests that by raising the intracellular level of cyclic AMP the luteinizing hormone inhibits the division of luteal cells and is not, for that reason, a mitogenic agent. A similar effect was obtained with other agents known to stimulate cyclic AMP production such asthe prostaglandins. Steroids such as glucocorticoids and testosterone but not progesterone also inhibited the growth rate. It is concluded that luteinizing hormone by controlling the level of cyclic AMP within the luteal cells is responsible for the expression of the phenotype of the cells and the maintenance of differentiation.
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PMID:The morphological transformation and inhibition of growth of bovine luteal cells in tissue culture induced by luteinizing hormone and dibutyryl cyclic AMP. 16 87

The involvement of cyclic AMP in corticosteroidogenesis was investigated by using isolated adrenal cell column perfusion. Steroids were produced in response to 0.5, 1.0 and 5.0 mg of cyclic AMP/ml. Analysis of the shape of the response curves indicated an inverse relationship between rate of onset of steroid production and dose. A further increase in steroid production during the washout period after the 5 mg/ml dose was considered to indicate an intracellular inhibitory effect of cyclic AMP. Release of cyclic AMP into the perfusate only occurred in response to supramaximal steroidogenic doses of ACTH (adrenocorticotrophin). A connexion between dose and response was demonstrated over a narrow concentration range. Variation in the time-lag before cyclic AMP production and in the duration of the response was marked; further, no reproducible ratio of steroid output to cyclic AMP output was shown at any level of stimulation. These results are discussed together with those of other recent investigations. It is considered that these findings do not support an obligatory role for cyclic AMP as mediator of ACTH action in the adrenal.
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PMID:An investigation of the involvement of adenosine 3':5'-cyclic monophosphate in steroidogenesis by using isolated adrenal cell column perfusion. 17 85

In dispersed rat interstitial cells in vitro both natural and synthetic estrogens inhibited the action of pituitary luteinizing hormone (LH), as assessed by testosterone production. The estrogens also inhibited dibutyryl cyclic AMP induced steroidogenesis, suggesting that one point of inhibition could be distal to the formation of cyclic AMP in the cells. Diethyl stilbestrol and its clinically used sodium phosphate derivative (Honvol), also affected hormone-receptor interaction when tested with rat testicular homogenates. Among estradiol, estradiol benzoate, Honvol and diethyl stilbestrol only the latter at high concentration had toxic effects on Leydig cells as noted from loss of thier viability.
Steroids 1979 Feb
PMID:Direct inhibitory effects of estrogens on rat Leydig cells in vitro. 22 53

A 59-year-old previously oophorectomized woman underwent surgery for a recurrent malignant granulosa cell tumor. Specimens and dispersed cells from the tumor tissue were incubated for 2 hr and cultured for 48 hr, respectively, with and without gonadotropins. Steroids and cyclic AMP (cAMP) concentrations were measured in the incubation and culture media. Incubated specimens from the tumor tissue released measurable amounts of cAMP, progesterone, and estradiol into the medium. Human follicle-stimulating hormone (FSH) 1 microgram/ml significantly stimulated the formation of cAMP and both steroids. Human luteinizing hormone (LH) 1 microgram/ml stimulated cAMP and progesterone but not estradiol release. Human chorionic gonadotropin (hCG) 10 micrograms/ml stimulated cAMP and progesterone formation in tumor tissue but was totally devoid of effect on estradiol release. In the tissue culture experiments progesterone and estradiol were formed in considerable amounts, with a higher capacity for progesterone than for estradiol. Progesterone formation was stimulated by FSH and hCG, while estradiol release was stimulated only by hCG. The addition of testosterone significantly enhanced estradiol formation in both incubation and culture experiments. It is concluded that the steroidogenesis of this granulosa cell tumor is sensitive to gonadotropins.
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PMID:Human granulosa cell tumor: stimulation of steroidogenesis by gonadotropins in vitro. 184 99

Cellular regulation by hormones that utilize a myriad of intracellular signaling pathways is recognized to be quite complex. To investigate some of these effects in an established cell line, we tested a panel of hormones and modulators for their effects on cyclic AMP (cAMP) and progesterone production, both alone and in combination with human chorionic gonadotropin (hCG), using the MA-10 cultured Leydig tumor cell line. None significantly affected intracellular levels of cAMP, and only epidermal growth factor (EGF) and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) stimulated progesterone production. While EGF, basic fibroblast growth factor, insulin, insulin-like growth factor-1, and transforming growth factor beta all decreased cAMP production only, TPA decreased hCG-stimulated cAMP and progesterone production. Those factors that stimulated progesterone production also induced a characteristic morphological change ("rounding") of these cells. In addition, EGF, insulin, and TPA, like hCG, elevated mRNA levels of competence oncogenes (c-fos and c-myc), albeit to different extents. These data demonstrate the wide range of hormones to which the cultured Leydig tumor cell will respond, as well as the varying degree of responses observed in the intracellular signaling pathways that we examined.
Steroids 1989 Dec
PMID:Effects of hormones and intracellular mediators on differentiated functions of cultured Leydig tumor cells. 255 32

Using the isolated perfused rabbit and rat ovaries as experimental models, we have studied various biochemical aspects of the ovulatory process. In rabbits, ovulations were induced by injecting hCG prior to the perfusion or by adding LH directly to the medium. In PMSG-treated rats, ovulations were induced by adding LH to the perfusion system. Steroids and other metabolites were analyzed in the perfusate and in follicular fluid. Steroid levels in follicular fluid were high early in the preovulatory development, but declined to very low levels 4 hours after LH stimulation. Levels of prostaglandins E and F rose as ovulation approached. In both perfusion models, indomethacin blocked ovulation without affecting steroid release or oocyte maturation. In the rabbit, PGF2 alpha reversed the indomethacin-induced inhibition and was able to induce follicular rupture by itself. Manipulations of the follicular fluid content of progesterone and estradiol to supraphysiological levels did not affect follicular rupture or oocyte maturation in the rabbit model. When the initial increase in LH-induced steroidogenesis was blocked by a 3 beta-ol-dehydrogenase inhibitor, ovulation was not affected. In rats, inhibition of estradiol production by an aromatase blocker did not affect the ovulatory process. When the endogenous formation of cyclic AMP is increased by pretreatment with a phosphodiesterase inhibitor, the LH-induced ovulation frequency increases in rabbits. Furthermore, forskolin, which increased the adenylate cyclase activity, stimulated steroidogenesis and induced follicular rupture. Recent experiments in the rat indicate that cyclic AMP acts on the ovulatory process via an effect on prostaglandin synthesis.
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PMID:Studies on the mechanism of ovulation using the model of the isolated ovary. 284 38

Removal of free calcium ions from the incubation medium of isolated bovine adrenocortical cells with EGTA reduced basal cortisol synthesis and blocked the effects of ACTH; additional calcium restored normal steroid synthesis. Calcium channel blockers, verapamil and nitrendipine and the calmodulin antagonist, trifluoperazine inhibited ACTH-stimulated cortisol synthesis in a dose-dependent manner (IC50s of 6.2, 10 and 5.2 microM, respectively). Steroidogenic effects of dibutyryl cyclic AMP were prevented with 50 microM verapamil or trifluoperazine. Calcium ionophore A23187 at 1 microM increased cortisol synthesis 2-3 fold which was less than the normal response to ACTH. Stimulatory effects of ionophore and cyclic AMP or ACTH were not additive. ACTH-stimulation of cortisol synthesis appears to involve cyclic AMP-dependent uptake of extracellular calcium ions, possibly by a mechanism requiring calmodulin. Increases in intracellular calcium ions cannot wholly mimic ACTH actions.
Steroids 1985 Jun
PMID:The role of calcium ions in the mechanism of ACTH stimulation of cortisol synthesis. 301 30

Using cultured Y-1 mouse adrenal tumor cells which produce 20 alpha-hydroxy-4-pregnen-3-one (20-DHP), it was found that 0.01 mM corticosterone and deoxycorticosterone increased basal and inhibited ACTH-induced 20-DHP production during consecutive 30 and 120 min incubations. Steroid effects were concentration-dependent and reversible. Six other steroids tested did not stimulate 20-DHP production and varied in ability to inhibit ACTH-stimulated steroidogenesis. Experiments demonstrated that 20-DHP production following treatment with cholera toxin, N,0'-dibutyryl cyclic AMP (dbcAMP), or pregnenolone was not inhibited by exogenous steroids. Corticosterone (0.01 mM) increased basal and inhibited ACTH-induced intracellular cyclic AMP (cAMP) production. Cytochalasin D, a microfilament perturbing agent, inhibited steroid-stimulated 20-DHP production, suggesting that ACTH and steroid stimulation mechanisms were similar. These findings taken together suggest that exogenous steroids can alter steroidogenesis by modifying plasma membrane adenylate cyclase activity.
Steroids 1985 Jul
PMID:Exogenous steroids alter steroidogenesis in cultured Y-1 adrenal tumor cells by actions preceding cyclic AMP. 301 50


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