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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sources of cholesterol for steroid hormone production were examined using bovine adrenocortical (BAC) cells in primary culture. The experiments were designed to determine the effects of lipoproteins on cortisol production and the level of BAC cell 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Most studies on BAC cell lipoprotein requirements have been conducted using human low-density lipoprotein (hHDL); none have used the homologous bovine lipoproteins. BAC cells treated with corticotropin (ACTH) in a medium devoid of lipoproteins increased and maintained cortisol production 7- to 20-fold above basal levels. Under such conditions ACTH also increased the rate of HMG-CoA reductase activity. Inhibition of HMG-CoA reductase with mevinolin inhibited cortisol production by 85%, indicating that the cells were using cholesterol synthesized de novo for steroid production. Cortisol production was increased almost 40-fold above basal levels if hLDL (100 micrograms/ml) was included in the incubation medium. Human LDL also suppressed the levels of HMG-CoA reductase in a concentration-dependent fashion. Human HDL was without effect on either BAC cell steroidogenesis of HMG-CoA reductase. Addition of bovine LDL (bLDL) to the incubation medium also caused an increase in cortisol production and inhibited cholesterol synthesis. By contrast to hHDL, bHDL (100 micrograms/ml) increased the ability of BAC cells to produce cortisol production. Bovine HDL (bHDL) also was able to decrease HMG-CoA reductase, but not to the extent caused by hLDL or bLDL. These data demonstrate that bovine adrenal cells can use bHDL as a source of cholesterol for steroid hormone production. These findings may be of particular importance when one considers that in vivo, the bHDL content of bovine serum greatly surpasses the level of bLDL.
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PMID:The role of bovine lipoproteins in the regulation of steroidogenesis and HMG-CoA reductase in bovine adrenocortical cells. 132 89

The sexually differentiated microsomal enzyme steroid 5 alpha-reductase (NADPH: delta 4-3-oxosteroid 5 alpha-oxido-reductase, EC 1.3.99.5) catalyzes the NADPH-dependent conversion of testosterone to 5 alpha-dihydrotestosterone, a more potent androgen. In rat liver, this enzyme is expressed at a 10-fold higher level in adult females as compared to adult males. The pituitary regulation of this enzyme and its mRNA was studied in untreated and hypophysectomized rats and in rats rendered hypothyroid by treatment with the antithyroid drug methimazole. Hepatic 5 alpha-reductase activity was elevated 8-fold, to 85% of adult female levels, in adult male rats given growth hormone by continuous infusion. This same treatment was only partially effective in restoring 5 alpha-reductase in rats depleted of endogenous growth hormone by hypophysectomy, indicating that other pituitary-dependent factors contribute to the elevation observed in the inact animals. Further analysis revealed that thyroxine, but not adrenocorticotropic hormone (ACTH) or chorionic gonadotropin, could elevate 5 alpha-reductase activity and mRNA when given to the hypophysectomized rats and that this effect was enhanced by the presence of growth hormone. This thyroid hormone dependence was confirmed by the decrease in hepatic 5 alpha-reductase expression in hypothyroid rats and by its substantial restoration following thyroxine replacement. Thyroxine also stimulated expression of another female-predominant hepatic mRNA, encoding the steroid 16 alpha-hydroxylase cytochrome P-450f (IIC7), in a manner that was independent of the stimulatory effect of growth hormone on this transcript. In contrast, thyroid hormone did not significantly affect protein or mRNA levels of the growth hormone-stimulated, female-specific steroid sulfate 15 beta-hydroxylase P-450 2d (IIC12). These findings establish that thyroid hormones act at a pretranslational level to modulate the expression of some, but not all, growth hormone-stimulated hepatic mRNAs and demonstrate that both thyroxine and growth hormone can independently contribute to the sex-dependent expression of hepatic enzymes of steroid metabolism.
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PMID:Pretranslational control by thyroid hormone of rat liver steroid 5 alpha-reductase and comparison to the thyroid dependence of two growth hormone-regulated CYP2C mRNAs. 217 47

Intracellular sources of extramitochondrial corticoidogenic cholesterol in bovine, rat and hamster adrenocortical cells were examined in vitro by comparing the species differences in the effects of various inhibitors on the adrenocorticotropic hormone (ACTH)-induced corticoidogenesis. The inhibitors were ML-236B (3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor), W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide; calmodulin inhibitor), dichlorvos (O,O-dimethyl-2,2-dichlorovinyl phosphate; organic phosphorylation inhibitor), chloroquine [7-chloro-4-4-diethylamino-1-methyl-butylamino) quinoline; lysosomal enzyme inhibitor) and cycloheximide (protein synthesis inhibitor). During 2 to 3 hr incubation periods, the ACTH-induced corticoidogenesis was not inhibited by ML-236B (100 microM) in the bovine and rat adrenocortical cells. In the hamster adrenocortical cells, ML-236B (100 microM) did not affect the ACTH-induced corticoidogenesis during the initial 1 hr incubation periods; but thereafter, the ACTH-induced corticoidogenesis during the subsequent 2 hr incubation periods was completely blocked by ML-236B. The ACTH-induced corticoidogenesis was inhibited by W-7 (up to 25 microM) in the bovine and rat adrenocortical cells, but this was not the case in the hamster cells. Chloroquine (up to 400 microM) inhibited the ACTH-induced corticoidogenesis in the adrenocortical cells of three different species, but the hamster adrenal cells were much more vulnerable than the bovine and rat cells. The ACTH-induced corticoidogenesis in the adrenocortical cells of three different species were equally inhibited by cycloheximide (up to 1 mM).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Sources of extramitochondrial corticoidogenic cholesterol in the adrenal cortex. 299 19

An 11-year-old patient with male pseudohermaphroditism presented with essentially normal-appearing female external genitalia. When examined, inguinal gonads, redundant foreskin, and some posterior labial fusion were found. Evaluation revealed basal testosterone (T) levels ranging from 65 to 107 ng/dl with slightly elevated serum gonadotropin levels (luteinizing hormone [LH]: 76 ng/ml, and follicle-stimulating hormone [FSH]: 568 ng/ml). Neither T nor its precursors increased with human chorionic gonadotropin (hCG) stimulation. However, progesterone (P), 17-hydroxyprogesterone (17-OHP), and cortisol (F) responses to adrenocorticotropic hormone (ACTH) were normal. Androgen binding and 5 alpha-reductase activity in cultured genital skin fibroblasts were normal. These data, plus the microscopic finding of a markedly reduced number of Leydig cells, strongly suggest that the male pseudohermaphroditism in this patient was due to inadequate Leydig cell function unrelated to LH receptors.
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PMID:Leydig cell hypofunction resulting in male pseudohermaphroditism. 628 Oct 87

Adrenal secretory rates of cortisol and arterial concentrations of adrenocorticotropin (ACTH) were measured in conscious trained dogs subjected to intravenous infusion of ACTH. To investigate the causal relation of ACTH to the secretion of cortisol, a mechanistic mathematical model based on current hypotheses of adrenocortical function was constructed and tested. It is widely believed that ACTH stimulates cortisol secretion through adenosine 3',5'-cyclic monophosphate (cAMP), which provides substrate cholesterol by activating cholesterol ester hydrolase and facilitating transport of cholesterol to the side-chain cleavage enzyme. In addition, cholesterol modulates its own synthesis by inhibiting beta-hydroxy-beta-methylglutaryl (HMG)-CoA reductase in the adrenocortical cell. These and other steps in the biosynthetic reaction sequence were described using differential equations subject to the additional constraints imposed by available measurements of intracellular quantities. The resulting model is consistent with many of the known characteristics of the canine adrenal response to ACTH. In this model, steady-state nonlinearities arise from cooperative binding of cAMP to its receptor protein and saturation of mitochondrial pregnenolone transport. The transient response is dominated by a depletable pool of intracellular free cholesterol. Other inferences based on the model are presented, and a quantifiable cellular basis for increased adrenal sensitivity to ACTH is proposed.
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PMID:A mechanistic model of ACTH-stimulated cortisol secretion. 632 2

The metabolism of testosterone and 5 alpha-dihydrotestosterone has been studied in vitro in preputial glands of posterior hypophysectomized, totally hypophysectomized and control sham-operated rats. The level of C19 steroid 5 alpha-reductase activity/unit of preputial gland DNA did not fall after removal of the neurointermediate lobe and rose after total hypophysectomy. It was concluded from this that the androgen unresponsiveness of the preputial glands of hypophysectomized rats was not due to a near-total lack of 5 alpha-reductase and hence that the combined synergistic action of testosterone and alpha-melanocyte-stimulating hormone (alpha-MSH) on preputial gland activity was unlikely to be due to an alpha-MSH-mediated restoration of 5 alpha-reductase levels in hypophysectomized rats. Levels of 3 alpha and 3 beta-hydroxysteroid dehydrogenase but not of 17 beta-hydroxysteroid dehydrogenase appeared to be altered by hypophysectomy.
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PMID:Mechanism of action of alpha-melanocyte-stimulating hormone in rat preputial glands: the role of androgen metabolism. 710 14

Simvastatin is an inhibitor of 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase, the key enzyme in the synthesis of cholesterol, recently introduced in the therapy of hypercholesterolemic patients. Cholesterol is the precursor of the biosynthesis of steroid hormones; thus, a reduction of the availability of cholesterol in the adrenal and testicular cells may reduce the synthesis of corticosteroids and androgens. To establish whether chronic therapy with simvastatin interferes with the integrity of the hypothalamic-pituitary-adrenal axis and with the adrenal and testicular reserve, we administered simvastatin orally in a single-day 10 mg dose for 6 months in 8 mildly hypercholesterolemic male patients. At weeks 0, 6 and 24 of treatment we evaluated the lipids, the activity of the hypothalamic-pituitary-adrenal axis by means of the Corticotropin-Releasing Hormone (CRH) test, the adrenal reserve by means of the Corticotropin rapid test and, finally, the testicular reserve by means of the Human Chorionic Gonadotropin (HCG) test. Total cholesterol and LDL-cholesterol were significantly reduced by Simvastatin, while the HDL-cholesterol and triglycerides did not change significantly. The hormonal responses to CRH, ACTH and HCG tests at weeks 6 and 24 of treatment were comparable to those obtained in basal conditions. We conclude that Simvastatin, while effective in reducing total and LDL-cholesterol in hypercholesterolemic male patients, did not interfere with hypothalamic-pituitary-adrenal axis activity or with basal and stimulated adrenal and testicular steroidogenesis.
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PMID:Effects of long-term simvastatin treatment on testicular and adrenal steroidogenesis in hypercholesterolemic patients. 793 Mar 73

Finasteride, a 5 alpha-reductase inhibitor, does not bind to the androgen receptor and has no other known hormonal activity. To determine what effect, if any, it has on adrenal steroidogenesis, 10 healthy men received 5 mg finasteride daily for 28 days. Adrenocorticotropic hormone (ACTH) stimulation tests were performed before and after 4 weeks of finasteride administration (5 mg daily). Serum levels of 17-hydroxypregnenolone, 17-hydroxyprogesterone, deoxycorticosterone, corticosterone, aldosterone, cortisol, dehydroepiandrosterone, and androstenedione were measured before and 60 minutes after i.v. ACTH. Finasteride decreased serum dihydrotestosterone levels from 31 +/- 5 to 4.4 +/- 1.2 ng/dl (P < 0.001). There were no significant changes in basal or ACTH-stimulated serum levels of adrenal steroids. There was also no significant decrease in the product to precursor ratio for the seven adrenal enzymes tested. Finasteride increased mean serum androstenedione levels by 17% (P = 0.10) and significantly increased the androstenedione to 17-hydroxyprogesterone ratio (P = 0.02 before ACTH and 0.05 after ACTH). These changes are most likely due to inhibition of androstenedione metabolism by 5 alpha-reductase. In conclusion, finasteride has no detectable effect on adrenal steroidogenesis, other than that which can be explained by inhibition of the 5 alpha-reductase enzyme.
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PMID:Effect of finasteride on adrenal steroidogenesis in men. 798 96

An oral 5-mg dose of finasteride, a 5 alpha-reductase inhibitor, was administered for 3 months to 10 hirsute women to determine the effect on gonadotropin secretion, on basal and stimulated androgen secretion, and on hair growth. Hair growth was assessed by the Ferriman-Gallwey score. All of the above determinations were evaluated before and after 1 and/or 3 months of finasteride treatment. Basal and GnRH-stimulated gonadotropin secretions were not affected. Indeed, finasteride did not modify the pulsatility of LH secretion. No change was seen in estradiol, PRL, free testosterone, androstenedione, dehydroepiandrosterone sulfate, and sex hormone-binding globulin concentrations. Serum concentrations of cortisol (F) were significantly reduced after 1 month of finasteride treatment. The F levels returned to pretreatment levels after 3 months. Plasma levels of dihydrotestosterone and 3 alpha-androstanediol glucuronide significantly decreased during finasteride treatment. A significant increase in testosterone concentrations was observed after 3 months. Finasteride did not modify the responses of testosterone, androstenedione, and dehydroepiandrosterone sulfate to ACTH-(1-24) injection. Conversely, finasteride blunted the F response to corticotropin stimulation. Three months of finasteride treatment significantly decreased the Ferriman-Gallwey score. In conclusion, finasteride significantly decreased dihydrotestosterone and hair growth in hirsute women without negatively affecting gonadotropin secretion.
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PMID:Effects of finasteride, a 5 alpha-reductase inhibitor, on circulating androgens and gonadotropin secretion in hirsute women. 807 69

Clinical and hormonal responses to a standard three-day human chorionic gonadotropin (hCG)-stimulation test (1,500 IU given intramuscularly for three days) were studied in six neonates with ambiguous genitalia. All patients were eventually determined to be 46,XY genetic males with a microphallus and various other genital abnormalities. None had an enzymatic defect in steroidogenesis or a 5 alpha-reductase deficiency, as determined by standard adrenocorticotropic hormone (ACTH) and hCG testing. All patients demonstrated penile growth (0.25 to 0.75 cm) within five days of hCG administration, with four of six patients achieving a normal penile length (> 2.0 cm) by 48 hours after the last of three daily hCG injections. Androgen responsiveness suggested by phallic growth may help support a male sex assignment in such infants.
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PMID:Phallic growth after hCG. A clinical index of androgen responsiveness. 839 54


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