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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Enzymatically dispersed rat pituitary cells were grown in primary culture, and LHRH-stimulated LH secretion was measured. Testosterone (T) decreased and 17 beta-estradiol (E) increased pituitary responsiveness to LHRH. The effect of E on LH secretion was partly due to an increase in LH content. There was a latent period of 12 h for E and 18 h for T between the onset of steroid treatment and the manifestation of steroid action. Neither steroid was required to be continuously present in order to exert its effects. After steroid withdrawal, the effect of T persisted for 72 h and that of E for more than 96 h. The actions of both steroids were blocked by protein-synthesis inhibitors. These results are consistent with the hypothesis that steroid effects rely on a mechanism involving alterations in protein synthesis; the affected proteins may be involved in the process of LHRH action.
Mol Cell Endocrinol 1982 Apr
PMID:Gonadal steroid modulation of LHRH-stimulated LH secretion by pituitary cell cultures. 628 70

The number of testosterone binding sites present in rat uterine cytosol varied regularly during the estrous cycle, reaching a trough at metestrus and a peak at proestrus. Treating ovariectomized and adrenalectomized rats for 2 days with estradiol resulted in a 3-4-fold increase in the number of binding sites per uterus. Estradiol withdrawal induced a decrease in uterine androgen receptors. Testosterone or progesterone treatment also increased the number of these sites, but to a lesser degree. When administered together with estradiol, testosterone did not enhance the stimulatory effect of the latter, whereas progesterone even reduced it. Testosterone or progesterone did not prevent the number of receptors from declining after estradiol withdrawal. Thus the changes in the number of cytoplasmic androgen receptors in the uterus during the rat estrous cycle is mainly controlled by the rise and fall of the serum levels of estradiol.
Mol Cell Endocrinol 1983 Mar
PMID:Variation of cytoplasmic rat uterine androgen receptors. 668 85

We have studied the hormonal control of prolactin (PRL) binding in the male rat sex glands and liver, subsequent to the recent demonstration and characterization of specific PRL binding sites in rat testis, prostate and seminal vesicle. Ovine PRL (200 micrograms/rat/day, 7 days) caused a time-dependent reduction in testicular binding of 125I-labelled PRL (measured 2 days after last injection) to 58% of control. Testosterone alone (1 mg/rat/day, 7 days) or PRL caused similar reductions in binding, while their coadministration further lowered PRL binding to 10% of control. The synergism of PRL and testosterone suggests that either these doses are submaximal, or that they are acting on different systems. Estradiol was administered as a single dose of 2 mg/rat and the PRL binding determined on day 10 and day 19 was reduced to 37% of control, as after testosterone. Addition of PRL whether from day 1 to day 7 or from day 11 to day 17 of estradiol injection had no effect, suggesting that the EB site of action is closer to the PRL receptor than that for PRL or testosterone. Estradiol resulted in a 72% reduction of PRL binding in the prostate, after 10 days, which subsequent PRL completely restored. PRL also partially restored the estradiol-induced time-dependent weight reduction of the prostate, but PRL coadministered from day 1 of estradiol did not inhibit the estradiol effects, suggesting a competitive mechanism for the two. While testosterone more than doubled PRL binding in the seminal vesicle, estradiol reduced it by 32% and organ weight by 21%. PRL given after estradiol restored the weight loss, but not the binding, suggesting that two different mechanisms of action are involved. In the liver, coadministration of testosterone with PRL could not inhibit the induction by PRL of its own hepatic sites, in keeping with a more direct site of action for PRL than for testosterone. These results demonstrate the profound effects of PRL, and of the sex steroids testosterone and estrogen, on PRL binding in the male sex glands and liver. The physiological implication of these findings on the role of PRL in male sexual function is currently being investigated.
Mol Cell Endocrinol 1983 May
PMID:Effect of prolactin, testosterone and estrogen on prolactin binding in the rat testis, prostate, seminal vesicle and liver. 685 62

We have carried out further in vitro studies on the priming effect of LH-RH and the effect of steroids on pituitary responsiveness to LH-RH. In hemipituitary glands, the priming effect could be elicited only once within an 11-h period and was found to diminish significantly with time after the first exposure to LH-RH. Incubation with oestradiol-17 beta (E2) had no significant effect on the responsiveness of hemipituitary glands to LH-RH. By contrast, E2 increased the responsiveness of dispersed cell system. The presence of hypothalamus or synthetic LH-RH did not facilitate the effects of E2. Testosterone significantly reduced the spontaneous and LH-RH-induced release of LH while progesterone had no effect. Exposure to E2 alone in either of the systems did not produce a consistent increase in the total amount of LH in the system. Synthesis of LH was, however, stimulated by exposure to LH-RH for 48 h but not 12 h. These results demonstrate that there is a marked difference between the mechanisms by which LH-RH and steroids affect the responsiveness of the anterior pituitary gland to LH-RH.
Mol Cell Endocrinol 1981 Dec
PMID:Comparison of steroid and LH-RH effects on the responsiveness of hemipituitary glands and dispersed pituitary cells. 703 50

The in vitro effects of progesterone, testosterone and estradiol-17 beta on steroid accumulation by isolated rabbit follicles were examined. Progesterone had no effect on LH-stimulated androgen accumulation but inhibited LH-stimulated estrogen accumulation at 10(-7) M and 10(-6) M. Testosterone at 10(-5) M but not at 10(-6) M or 10(-7) M, inhibited LH-stimulated progesterone accumulation. LH-stimulated estrogen accumulation was inhibited at all dose levels of testosterone. Estradiol (10(-5) M) inhibited LH-stimulated androgen accumulation and had no effects on progesterone accumulation. It is concluded that the steroidal milieu of follicles can influence their response to LH.
Mol Cell Endocrinol 1982 Apr
PMID:In vitro effects of sex steroids on LH-stimulated steroid accumulation by isolated rabbit ovarian follicles. 708 61

Mitochondria (m-)aconitase is a rate-limiting regulatory enzyme in prostate epithelial cells which minimizes citrate oxidation by these cells. This unique metabolite characteristic is responsible for the ability of the prostate to accumulate and secrete extraordinarily high levels of citrate. Testosterone is a major regulator of prostate growth and function, and stimulates citrate oxidation. Therefore, an important action of testosterone might be its stimulation of m-aconitase in prostate epithelial cells. Studies were conducted with rat ventral prostate (VP) epithelial cells to establish the effect of testosterone on the level of m-aconitase and corresponding citrate oxidation. Physiological concentrations (10(-7)-10(-10) M) of testosterone in vitro markedly increased the level of m-aconitase in freshly prepared isolated prostate epithelial cells. This increase was apparent within 3 h of exposure to the hormone. The stimulatory effect of testosterone on m-aconitase was abolished by actinomycin D and by cycloheximide. Both the level of m-aconitase enzyme and the level of m-aconitase activity were similarly increased by testosterone treatment. Correspondingly, testosterone increased the rate of mitochondrial citrate oxidation while having no effect on the rate of isocitrate oxidation, thereby demonstrating that the action of testosterone is specifically targeted at the m-aconitase reaction. In vivo studies revealed that castration markedly decreased and testosterone administration increased the m-aconitase level of prostate epithelial cells. In contrast, neither liver nor kidney m-aconitase level was altered by castration. These studies demonstrate that testosterone regulates the biosynthesis of m-aconitase in prostate epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1995 Jul
PMID:Testosterone stimulates the biosynthesis of m-aconitase and citrate oxidation in prostate epithelial cells. 758 84

Testosterone, the principal androgen secreted by Leydig cells, exerts a wide range of actions including growth of the male reproductive tract (androgenic effects) and growth of non-reproductive tissues such as muscle, kidney, liver, and salivary gland (anabolic effects). As androgenic steroids were discovered some were found to have relatively more anabolic than androgenic activity. The results reviewed in this report suggest that these differences result, in part, from the differential metabolism of the steroids in individual tissues and the varied activities of the individual metabolites. In the accessory sex organs (e.g. the prostate) testosterone is 5 alpha-reduced to dihydrotestosterone (DHT) which, due to its higher affinity for androgen receptors (AR), amplifies the action of testosterone. In contrast, when 19-nortestosterone (NT) is 5 alpha-reduced, its affinity for AR decreases, resulting in a decrease in its androgenic potency. However, their anabolic potency remains unchanged since significant 5 alpha-reduction of the steroids does not occur in the muscle. 7 alpha-methyl-19-nortestosterone (MENT) does not get 5 alpha-reduced due to steric hindrance from the 7 alpha-methyl group. Therefore, the androgenic potency of MENT is not amplified as happens with testosterone. These metabolic differences are responsible for the increased anabolic activity of NT and MENT compared to testosterone. Part of the biological effects of testosterone are mediated by its aromatization to estrogens. The fact that MENT is also aromatized to 7 alpha-methyl estradiol, a potent estrogen, in vitro by human placental and rat ovarian aromatase suggests that some of the anabolic actions of MENT may be mediated by this estrogen.
J Steroid Biochem Mol Biol 1995 Jun
PMID:Different patterns of metabolism determine the relative anabolic activity of 19-norandrogens. 762 64

The mechanisms by which the sex hormones achieve their bone-sparing effects remains unresolved. Interleukin-1 beta (IL-1 beta) is an autocrine/paracrine regulator of bone that may be produced in an estrogen-sensitive manner. The regulation of IL-1 beta production by the gonadal steroids was tested in the human osteoblastic HOBIT cell model. Dose-dependent 4-8-fold increases (P < 0.05) in IL-1 beta mRNA levels followed a 6-48 h treatment with 17 beta-estradiol or testosterone. Receptor mediation of these responses was indicated by experiments using 17 alpha-estradiol or flutamide. Tumor necrosis factor-alpha (TNF) dependent increase IL-1 beta mRNA levels were additive to the effects of the steroids. Testosterone and TNF increased IL-1 beta protein release (P < 0.05) while 17 beta-estradiol had little effect on release. The bone-sparing effects of the gonadal steroids may be accomplished, in part, through their mediation of local IL-1 beta production.
Mol Cell Endocrinol 1995 Apr 28
PMID:Sex hormones mediate interleukin-1 beta production by human osteoblastic HOBIT cells. 764 54

In this report, we describe the effects of a recently described atrial natriuretic peptide (ANP) antagonist, HS-142-1, on the action of ANP on Percoll-purified mouse Leydig cells. Incubation of the Leydig cells with 10(-8) M ANP for 3 h resulted in a 16-fold stimulation of testosterone production over basal. Addition of HS-142-1 in a concentration range of 0.1 to 5 micrograms/ml resulted in a dose-dependent inhibition of ANP-induced testosterone production, a nearly complete inhibition being achieved with 5 micrograms/ml antagonist. Testosterone production by unstimulated cells or in cells stimulated with hCG was not affected by the antagonist. HS-142-1 was also able to inhibit the ANP-stimulated cyclic guanosine monophosphate (GMP) formation in the cells, in a dose-dependent manner. However, cyclic AMP level in cells stimulated with either forskolin or hCG remained unaffected by HS-142-1 even when added at a concentration of 5 micrograms/ml. Results obtained from 125I-ANP binding experiments showed that HS-142-1 is able to competitively inhibit the binding of the radioligand to its receptors on the Leydig cells. Thus evidence obtained in this study permit us to conclude that HS-142-1 is a potent and specific antagonist of ANP, has no toxic effect on the cells and is able to inhibit competitively the binding of ANP to its guanylate cyclase coupled receptors. Availability of such antagonists are likely to facilitate research on the physiology of ANP.
Mol Cell Endocrinol 1993 Jul
PMID:HS-142-1 inhibits testosterone production and guanosine-3':5'-cyclic monophosphate accumulation stimulated by atrial natriuretic peptide in isolated mouse Leydig cells. 769 Jul 21

The objective of this study was to define the factors regulating the endogenous production of sulfated glycoprotein-1 (SGP-1) in nonciliated cells of the efferent ducts. To this end we examined five different groups of animals undergoing the following experimental procedures: (1) hypophysectomized animals at 7, 14, and 28 days, (2) 7-day hypophysectomized rats receiving testosterone implants given at various time intervals thereafter, (3) castration at various time intervals up to 7 days, (4) 7-day castrated rats receiving testosterone implants at various time intervals thereafter, and (5) castrated rats given testosterone implants immediately after castration and sacrificed at different time intervals thereafter. Efferent ducts were fixed by perfusion with 4% paraformaldehyde and 0.5% glutaraldehyde in phosphate buffer for quantitative immunocytochemical analysis at the level of the electron microscope. For each experimental condition and their controls, the number of gold particles/micron2 within the endosomal and lysosomal compartments was calculated taking into account the changes in both the volume of the cell and organelles being quantified and expressed as labeling content. The results revealed that hypophysectomy (up to 4 weeks) caused a marked significant decrease in the SGP-1 labeling content of the endosomal and lysosomal compartments. The labeling content of the lysosomal compartment of efferent ducts from rats castrated for up to 1 week did not change significantly. However, there was a significant decrease in the labeling content of endosomes. This decrease is due to SGP-1, which is secreted by Sertoli cells, not being available for uptake in the efferent ducts. These results suggested that testosterone is not required for maintaining the high labeling content of SGP-1 within lysosomes of nonciliated cells, but that a pituitary factor appears to be needed. The administration of testosterone at different intervals to 7-day castrated animals resulted in a significant decrease of lysosomal SGP-1, suggesting that testosterone under these experimental conditions inhibits the production of a pituitary factor that maintains the high labeling content of SGP-1 within lysosomes of the nonciliated cells. Testosterone administered to 7-day hypophysectomized animals over a 24-hr period had no effect on the labeling content of SGP-1 within lysosomes. However, the administration of testosterone to animals immediately following castration showed no differences in the labeling content of SGP-1 within compared to controls.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Reprod Dev 1995 Jan
PMID:Hormonal regulation of sulfated glycoprotein-1 synthesis by nonciliated cells of the efferent ducts of adult rats. 770 72


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