Potent antagonism between estrogens and androgens on GCDFP-15 expression and cell growth in the ZR-75-1 human breast cancer cells.
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Apolipoproteins↗
Biomedical subjects
F Labrie
Publications and source records attributed to F Labrie.
Interactions between estrogens, androgens, progestins, and glucocorticoids in ZR-75-1 human breast cancer cells.
The human breast cancer cell line ZR-75-1 possesses androgen, estrogen, progesterone, and glucocorticoid receptors, thus offering a good model to study the specific role of each class of steroids in the control of breast cancer growth. Although the stimulatory action of classical estrogens (E2 and estrone) is well known, we have found a potent mitogenic effect of the adrenal estrogen androst-5-ene-3 beta,17 beta-diol (delta 5-diol) at concentrations within the range of those found in the serum of adult women, thus suggesting that delta 5-diol might be the most important estrogen in women. Androgens, on the other hand, exert a potent inhibitory effect on basal ZR-75-1 cell growth and completely reverse the stimulatory effect of estrogens on the same parameter. The antiproliferative effect of androgens was completely prevented by the antiandrogen OH-FLU, thus suggesting an action mediated by the androgen receptor. Part of the effect of androgens can be explained by the marked inhibition of estrogen receptor binding and mRNA levels by androgens. The antiproliferative effect of androgens is additive to that exerted by antiestrogens. Progestins, on the other hand, exert a specific antiproliferative effect in the presence of estrogens, the effect of progestins being antagonized by the stimulatory action of insulin on cell growth. Medroxyprogesterone acetate (MPA), a compound frequently used in the treatment of breast cancer in women, exerts its main inhibitory action through an androgen receptor-mediated action, whereas its glucocorticoid-like activity could play an additional role at high concentrations. All four classes of steroids are present, to various extents, as lipophilic esters of long-chain fatty acids. It is of interest to mention that all steroids that inhibit ZR-75-1 breast cancer cell growth (androgens, progestins, and glucocorticoids) stimulate the secretion and mRNA levels of gross cystic disease fluid protein-15 (GCDFP-15), whereas estrogens have the opposite effects, thus suggesting that GCDFP-15 could well be a good marker for monitoring the response to androgens, progestins, and antiestrogens during the course of breast cancer therapy.
Androgens↗
Identification of a 51-kilodalton calmodulin binding protein that changes during estrogen-stimulated cell growth.
Calmodulin-binding proteins (CaMBPs) were analyzed during estrogen-stimulated growth in the human breast cancer cell line ZR-75-1. A variety of Ca2(+)-dependent and -independent CaMBPs were observed to be present in these cells. Calmodulin (CaM) binding to a 51-kilodalton protein was shown to be Ca2(+)-dependent. Moreover, binding to this protein was reduced in the estrogen-treated cells. This effect occurred early during estrogen-stimulated cell growth and was maintained during exponential growth in the presence of estrogen. 125I-labeled CaM overlay procedure of two-dimensional polyacrylamide gels reveals that this 51-kilodalton protein is composed of at least two distinct isoforms with different isoelectric points. Subcellular localization demonstrates that this protein resides exclusively in the microsomal fraction.
Breast Neoplasms↗
Model of the distribution and metabolism of a GnRH superagonist in dogs.
The plasma kinetics of [D-Trp6, des-Gly-NH2(10)]gonadotropin-releasing hormone (GnRH) ethylamide was assessed in eight dogs over a period of 8 h after rapid intravenous or subcutaneous injection. Each animal received doses of 0.2, 2, and 20 micrograms/kg body wt iv and 1 and 10 micrograms/kg body wt sc. A two-compartment structure, to which a source compartment was added to represent the subcutaneous route, adequately fits the five kinetics when the apparent volume of distribution follows a plasma concentration-dependent sigmoid function. Despite the nonlinearity, the apparent volume of distribution can be approximated by a constant value of 280 ml/kg body wt for the dynamics corresponding to the three lowest and more physiological doses. The metabolic clearance rate is 4.63 ml.min-1.kg body wt-1. The two exponential components that characterize the two-compartment structure are equal to 0.0348 +/- 0.0053 and 0.00470 +/- 0.00060 min-1, respectively. The agonist injected subcutaneously diffuses to plasma at a fractional rate of 0.0265 +/- 0.0029 min-1. Disposal occurs at a maximal rate of 0.017 and 0.0055 min-1 of the amount of agonist present in the central and peripheral compartments, respectively. The highest fractional exchange rate between compartments reaches 0.01 min-1. As simulated with the model, a continuous infusion of 4.63 ng.min-1.kg body wt-1 leads to a steady state of 1 ng/ml plasma; 90% of that level is reached 7 h after the onset of the subcutaneous input signal. The kinetics of plasma [D-Trp6, des-Gly-NH2(10)]GnRH ethylamide is many times slower than that of the native hormone and of the other GnRH agonists.
Animals↗
Effects of estrogens on the ultrastructural characteristics of female rat prolactin cells as evaluated by in situ hybridization in combination with immunogold staining technique.
We have recently reported that, in the rat pituitary, prolactin (PRL) is synthesized and stored in two different cell types: the typical PRL cell characterized by the presence of large irregular secretory granules and another cell type containing small round secretory granules. Since the secretion of PRL is stimulated by estrogens, we decided to investigate the effect of gonadectomy and estradiol (E2) replacement therapy in female rats on both cell types using a combination of in situ hybridization and immunostaining. Gonadectomy induced a marked decrease in hybridization signal and an almost complete disappearance of the classical PRL cells. The most abundant PRL cells were the small-granule-containing cells and other PRL cells characterized by the presence of both small and large granules. These changes in the PRL cell population were completely prevented by E2 administration to castrated animals. These studies indicate that E2 cannot only regulate PRL mRNA but also induce important morphological changes in PRL cell types.
Animals↗
Multihormonal control of pre-pro-somatostatin mRNA levels in the periventricular nucleus of the male and female rat hypothalamus.
The influence of sex steroids as well as the possible involvement of dopaminergic pathways in the modulation of pre-pro-somatostatin (SS) mRNA levels was investigated by quantitative in situ hybridization in the hypothalamic periventricular nucleus (PeN) in adult male and female rats. In situ hybridization was performed using a [35S]-labeled cDNA probe encoding pre-proSS mRNA. Gonadectomy performed 14 days earlier decreased the mean number of silver grains/neuron corresponding to the relative pre-proSS mRNA levels by 22% in male and by 18-28% in female rats. A 14-day treatment with the nonaromatizable androgen dihydrotestosterone (DHT) increased the mean number of silver grains/neuron by 34-40% in gonadectomized animals of both sexes. Moreover, administration of 17 beta-estradiol (E2, 0.25 microgram twice daily) increased pre-proSS mRNA levels by 40% in ovariectomized (OVX) animals. Such treatment with E2 or DHT changed the frequency distribution profile of the hybridization signal intensity, thus increasing the percentage of highly labeled neurons (greater than or equal to 61 grains/neuron) by 10 to 12-fold. A 14-day treatment with the D2 dopamine receptor agonist bromocriptine (BRO) increased pre-proSS mRNA levels by 15 and 28% in intact female and OVX animals, respectively, while the dopaminergic antagonist haloperidol (HAL) decreased the value of this parameter by 20 and 30%. Furthermore, BRO increased pre-proSS mRNA levels by 10 and 20% in intact and castrated male rats, respectively, whereas HAL decreased pre-proSS mRNA levels by 25 and 14% in the same groups of animals. Administration of E2 in combination with HAL in OVX animals increased pre-proSS mRNA levels by 70% compared to those measured in OVX animals treated with HAL alone. In HAL-treated castrated male rats, administration of DHT increased the relative pre-proSS mRNA levels by 35% compared to those measured in castrated animals treated with HAL alone. The present data clearly demonstrate that androgens and estrogens as well as dopamine-mediated mechanisms could play a regulatory role in pre-proSS mRNA levels in somatostatinergic neurons in the hypothalamic PeN in both male and female rats.
Animals↗
Effect of combined androgen blockade with an LHRH agonist and flutamide in one severe case of male exhibitionism.
A severe exhibitionist has been treated with the combination of an LHRH agonist and the antiandrogen flutamide in order to maximize androgen blocking and to control his severe deviant behaviour. The results obtained show that the androgen blockade ended his exhibitionistic behaviour and markedly decreased his sexual fantasies and activities, especially masturbation, without significant side effects.
Administration, Oral↗
Beta-adrenergic receptors in the rat mammary gland during pregnancy and lactation: characterization, distribution, and coupling to adenylate cyclase.
To investigate a possible role of catecholamines in mammary gland growth and differentiation, we have studied the characteristics of a specific beta-adrenergic receptor population during the different reproductive phases of the rat mammary gland, namely pregnancy and lactation. The functional response to mammary beta-adrenergic receptor stimulation was assessed by measurement of adenylate cyclase activity during the same physiological states of the gland [125I]Cyanopindolol (CYP) binds specifically to membranes prepared from lactating mammary glands. Scatchard analysis of the binding data shows the presence of a single class of high affinity sites, with an apparent Kd value of 25.0 +/- 0.4 pM and a binding capacity of 32.5 +/- 1.2 fmol/mg protein in lactating mammary glands at random stages of lactation. The order of potency of a series of agonists to compete for [125I]CYP binding is consistent with the interactions with a beta 2-subtype receptor. The binding of [125I]CYP to mammary glands also shows a marked stereoselectivity; the (-)isomers of isoproterenol and propranolol are more potent than their respective enantiomers. The radioautographic localization of [125I]CYP reveals the presence of specific beta-adrenergic receptors in the epithelial cells, alveoles, ducts, as well as adipocytes. [125I]CYP binding shows a 2- to 3-fold increase during pregnancy. Such a result correlates with parallel increases in stimulation of adenylate cyclase activity, the cytosolic progesterone receptor concentration, as well as plasma 17 beta-estradiol and progesterone levels. At parturition, a sharp decline in beta-adrenergic receptor concentration is observed, a finding concomitant with a drop in progesterone receptor levels as well as plasma estradiol and progesterone concentrations. During midlactation, beta-adrenergic receptors reach their maximal levels. The presence of specific beta-adrenergic receptors functionally coupled to the adenylate cyclase system and the marked changes in receptor capacity and distribution measured during the different physiological states of the mammary gland suggest that the mammary beta-adrenergic receptors are highly sensitive to changes in the hormonal milieu and provide a mechanism for a direct catecholaminergic influence on mammary gland growth and differentiation.
Adenylyl Cyclases↗
Hormonal regulation of beta-adrenergic receptors in the rat mammary gland during the estrous cycle and lactation: role of sex steroids and prolactin.
To gain further knowledge on the role of ovarian hormones in the regulation of mammary beta-adrenergic receptors, virgin animals were killed during the various phases of the estrous cycle as well as after ovariectomy and treatment with sex steroid. beta-Adrenergic receptor levels fluctuate in the rat mammary gland during the estrous cycle, with higher receptor numbers during the proestrous and estrous phases of the cycle. Ovariectomy caused an almost 50% loss of beta-adrenergic receptor concentration in the mammary gland of virgin rats. Treatment of ovariectomized animals with 17 beta-estradiol or progesterone alone or in combination for 3 weeks induced a marked increase in beta-adrenergic receptor concentration, while administration of the androgen dihydrotestosterone did not modify mammary beta-adrenergic binding sites. While levels of beta-adrenergic receptors in control lactating animals (10 days of lactation) were elevated, chronic treatment with the dopaminergic-mimetic agent 2 alpha-bromoergocryptine (CB-154; for 7 days) reduced beta-adrenergic receptor concentration. Castration of lactating animals decreased beta-adrenergic receptor number to approximately 30% of the value in intact controls, while combined withdrawal of circulating ovarian hormones and inhibition of plasma PRL levels caused an almost complete inhibition of beta-adrenergic receptor concentration. Scatchard analysis of the binding data revealed that the observed alterations in beta-adrenergic receptors resulted from changes in the number of beta-adrenergic binding sites, with no change in binding affinities. The present findings indicate that the beta-adrenergic receptor population of the rat mammary gland is under the control of ovarian hormones and PRL and suggest that circulating or locally released catecholamines could interact with sex steroids and PRL in the regulation of mammary gland growth, differentiation, and activity.
Animals↗
Evidence for the regulation of 3 beta-hydroxysteroid dehydrogenase messenger RNA by human chorionic gonadotrophin in luteinized porcine granulosa cells.
The effects of hCG on the abundance of messenger RNA for the steroidogenic enzyme 3 beta-hydroxysteroid dehydrogenase (3 beta-OHSD) were studied in luteinized porcine granulosa cells. There were dose-dependent increases in the mRNA for this enzyme after 8 h incubation with hCG or dibutyryl cAMP. The results suggest that LH-like hormones regulate the expression of the 3 beta-OHSD gene in luteinized tissue, and this genomic regulation is a component of the luteotrophic regulation of steroidogenesis in the ovary.
3-Hydroxysteroid Dehydrogenases↗
Light microscopic immunocytochemical localization of 3 beta-hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4-isomerase in the gonads and adrenal glands of the guinea pig.
The enzyme complex 3 beta-hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4-isomerase (3 beta HSD) is involved in the biosynthesis of all classes of active steroids, namely glucocorticoids, mineralocorticoids, progesterone, and sex hormone steroids. To obtain precise information about the cellular and subcellular localization of 3 beta HSD in the gonads and adrenals of the guinea pig, we have proceeded to immunocytochemical localization of the enzyme using antibodies developed against purified human placental 3 beta HSD. In the testis, specific immunostaining was restricted to the cytoplasm of the interstitial cells. In the ovary, on the other hand, immunostaining was found in the cytoplasm of the cells of the corpus luteum and theca interna. The granulosa cells of the follicles were not immunolabeled, with the exception of one layer of cells in contact with the zona pellucida. This restricted labeling was observed in growing and mature follicles, but not in primordial and small primary follicles. In the adrenals, the three zones of the cortex were labeled, whereas no staining could be detected in the medulla. Contrary to findings in the testis and ovary, staining was found in both the cytoplasm and nuclei of adrenocortical cells. The present data suggest a functional interaction between the ovocyte and the specialized layer of 3 beta HSD-containing granulosa cells which might play a role in ovocyte maturation.
3-Hydroxysteroid Dehydrogenases↗
Regulation of progesterone-binding breast cyst protein GCDFP-24 secretion by estrogens and androgens in human breast cancer cells: a new marker of steroid action in breast cancer.
We have previously demonstrated that androgens are potent inhibitors of breast cancer cell proliferation under both basal and estrogen-induced incubation conditions, while they suppress expression of the estrogen and progesterone receptors. To better understand the mechanisms responsible for the antagonism between androgens and estrogens in breast cancer and to obtain a new tumor marker for the actions of these two steroids, we have investigated the effects of androgens and estrogens on expression of the major protein found in human breast gross cystic disease fluid, namely GCDFP-24. This study was performed in ZR-75-1 and MCF-7 human breast cancer cells. After a 9-day incubation period, physiological concentrations of 17 beta-estradiol stimulated proliferation of ZR-75-1 and MCF-7 cells by 2- to 3.5-fold while simultaneously exerting a marked 70-90% inhibition of GCDFP-24 secretion. The estrogenic effects on GCDFP-24 secretion and cell proliferation were both competitively blocked by simultaneous incubation with the new steroidal pure antiestrogen EM-139. On the other hand, a maximal concentration (10 nM) of the nonaromatizable androgen dihydrotestosterone decreased by 50% the proliferation of ZR-75-1 cells; the half-maximal inhibitory effect was exerted at 0.01 nM. The androgen exerted a 3- to 4-fold stimulatory effect on GCDFP-24 secretion at an EC50 value of 0.01 nM. The effect of dihydrotestosterone on these parameters was competitively blocked by simultaneous incubation with the pure antiandrogen OH-flutamide. The present data show that the effects of estrogens and androgens in ZR-75-1 cells on GCDFP-24 secretion and cell growth are opposite. Similarly, in MCF-7 cells, estrogens stimulate cell growth, while GCDFP-24 secretion is inhibited. The present data also suggest that GCDFP-24 could well be a good biochemical marker for monitoring the response to androgenic and antiestrogenic compounds in the therapy of advanced breast cancer.
Androgens↗
Localization of 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase in rat gonads and adrenal glands by immunocytochemistry and in situ hybridization.
The enzyme complex delta 5-3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta HSD) is involved in the biosynthesis of all classes of steroids, namely glucocorticoids, mineralocorticoids, progesterone, and sex steroids. To obtain information on the precise localization of 3 beta HSD in rat gonads and adrenal glands, two complementary cytochemical techniques were used; immunocytochemical localization was achieved with antibodies developed against purified human placental 3 beta HSD, while 3 beta HSD mRNA localization was achieved by in situ hybridization performed with a recently cloned rat 3 beta HSD cDNA. In the testis, specific immunostaining was restricted to the cytoplasm of the interstitial cells, while by in situ hybridization, specific silver grains were also seen over the interstitial cells. In the ovary, immunostaining was found in the cytoplasm of cells of the corpus luteum and theca interna, while the granulosa cells of the follicles showed no positive reaction. By in situ hybridization, a specific hybridization signal was observed over granulosa cells of the corpus luteum, which are mainly responsible for progesterone secretion, and to a lesser extent over theca interna cells, known for their role in secreting C19 androgens. In the adrenals, the three zones of the cortex were equally immunolabeled, whereas no staining could be detected in the medulla. Similarly, by in situ hybridization, silver grains were located over the zona glomerulosa, fasciculata, and reticularis, while no specific autoradiographic reaction could be observed on the chromaffin cells of the medulla. The present study provides new information about the precise cellular localization of 3 beta HSD in the adrenal glands and gonads in the rat, thus providing useful information about the site of action of 3 beta HSD, especially in the gonads. Moreover, the approaches used for localization studies, especially quantitative in situ hybridization, should provide a useful tool for assessing the role of hormones on 3 beta HSD expression in the different compartments of the gonads and adrenal glands.
3-Hydroxysteroid Dehydrogenases↗
Changes in 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase messenger ribonucleic acid, activity and protein levels during the estrous cycle in the bovine ovary.
A 1169 base pair fragment of bovine 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) cDNA was used to quantitate 3 beta-HSD messenger RNA (mRNA) levels in the bovine ovary during the estrous cycle. The content of 3 beta-HSD protein was measured by immunoblot analysis using an antiserum developed in rabbits against human 3 beta-HSD, whereas 3 beta-HSD activity was measured using [3H]pregnenolone, [3H] dehydroepiandrosterone, and [3H]androst-5-ene-3 beta,17 beta-diol as substrates. There was a parallel increase in 3 beta-HSD mRNA, protein content, and enzymatic activity levels from days 1-3 after estrus to maximal values at 50-100% above control on days 8-11 after estrus. Thereafter, all values decreased progressively until days 16-17 before a dramatic fall to 5% or less than maximal values on days 18-20 after estrus. Almost superimposable results of enzymatic activity were obtained with the three substrates, thus suggesting a unique 3 beta-HSD or parallel changes in the activity of multiple 3 beta-HSDs. The above-described changes observed during the luteal phase are almost exclusively due to variations in corpora lutea. In fact, 3 beta-HSD activity in ovarian follicles was approximately 10,000 lower than that measured in corpora lutea. The close correlation observed over a wide range of 3 beta-HSD mRNA, protein content, and activity levels suggests that changes of ovarian 3 beta-HSD activity are controlled at the level of 3 beta-HSD gene expression and/or 3 beta-HSD mRNA stability.
Animals↗
Regulation of 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase expression and activity in the hypophysectomized rat ovary: interactions between the stimulatory effect of human chorionic gonadotropin and the luteolytic effect of prolactin.
The enzyme 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) catalyzes an obligatory step in the conversion of pregnenolone and other 5-ene-3 beta-hydroxysteroids into progesterone as well as precursors of all androgens and estrogens in the ovary. Since 3 beta-HSD is likely to be an important target for regulation by pituitary hormones, we have studied the effect of chronic treatment with LH (hCG), FSH, and PRL on ovarian 3 beta-HSD expression and activity in hypophysectomized adult female rats. Human CG (hCG) [10 IU, twice a day (bid)], ovine FSH (0.5 microgram, bid), and ovine PRL (1 mg, bid) were administered, singly or in combination, for a period of 10 days starting 15 days after hypophysectomy. In hypophysectomized rats, PRL exerted a potent inhibitory effect on all the parameters studied. In fact, PRL caused a 81% decrease in ovarian 3 beta-HSD mRNA content accompanied by a similar decrease in 3 beta-HSD activity and protein levels. In addition, ovarian weight decreased by 40% whereas serum progesterone fell dramatically from 1.92 nmol/liter to undetectable levels after treatment with PRL. Whereas hCG alone had only slight stimulatory effects on 3 beta-HSD mRNA, protein content and activity levels, treatment with the gonadotropin partially or completely reversed the potent inhibitory effects of oPRL on all the parameters measured. FSH, on the other hand, had no significant effect on 3 beta-HSD expression and activity. In situ hybridization experiments using the 35S-labeled rat ovary 3 beta-HSD cDNA probe show that the inhibitory effect of PRL is exerted primarily on luteal cell 3 beta-HSD expression and activity. On the other hand, it can be seen that hCG stimulates 3 beta-HSD mRNA accumulation in interstitial cells. The present data show that hCG and PRL exert potent and opposite cell-specific effects on ovarian 3 beta-HSD expression, activity, and content in the rat ovary. Moreover, the present study could suggest that female infertility associated with hyperprolactinemia in women could well be related, at least in part, to the potent inhibitory effect of PRL on ovarian 3 beta-HSD expression and activity.
3-Hydroxysteroid Dehydrogenases↗
Structure and sexual dimorphic expression of a liver-specific rat 3 beta-hydroxysteroid dehydrogenase/isomerase.
The enzyme 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) catalyzes the obligatory oxidation and isomerization of delta 5-3 beta-hydroxysteroid precursors into delta 4-3-ketosteroids which lead to the formation of all classes of steroid hormones. We report the molecular cloning of a third type of cDNA clone encoding rat 3 beta- HSD isolated from a rat liver lambda gt11 cDNA library. The nucleotide sequence of 1955 bp determined from overlapping cDNA clones predicts a protein of 372 amino acids which displays 80% similarity with that of rat type I and type II 3 beta-HSD proteins. RNA blot analysis reveals the presence of mRNA transcripts of 2.1 kb in male liver in contrast to the 1.7 kb mRNA species detected in adrenal and gonad poly(A)+ RNA. Ribonuclease protection assays using type I, type II and type III specific cRNA probes demonstrate the liver-specific expression of type III mRNA while the two others are expressed in adrenals and gonads. The type III mRNA species was below the detection limit in intact female liver while in hypophysectomized females, its accumulation was restored to 55% of the levels measured in intact or hypophysectomized male rats. The present data describe the presence of a third type of 3 beta-HSD mRNA species and its marked sexual dimorphic gene expression in the liver which apparently results from pituitary hormone-induced gene repression in female rat liver tissue.
Amino Acid Sequence↗
Model of the distribution and metabolism of the gonadotropin-releasing hormone (GnRH) agonist [D-Trp6,Des-Gly-NH2(10)]GnRH ethylamide in man.
The kinetics of plasma immunoreactive [D-Trp6,Des-Gly-NH2(10)]GnRH ethylamide, a potent GnRH agonist, was assessed in nine normal adult men over a period of 24 h after a rapid sc injection of 1 or 10 micrograms peptide/kg BW. The specific RIA of the GnRH agonist is characterized by a minimum detectable dose of 5.0 +/- 0.5 pg peptide, while the midrange effective dose is 73 +/- 8 pg. The within- and between-assay coefficients of variation range from 2-7% and from 10-15%, respectively. When the volume of the central compartment is set proportional to the logarithm of the plasma concentration of the GnRH agonist, the time courses of both doses are statistically well represented by a two-compartment model to which a source compartment is added to represent the sc route of administration. The sc diffusion to plasma is 5 times faster than any other fractional transport rate of the model (5%/min). Disposal occurs at a maximum rate of 0.55%/min from the central compartment, which includes plasma, and 0.25%/min from the peripheral compartment. As simulated with the model, 90% of the steady state is reached 13 h and 45 min after the onset of a sc continuous infusion. A molecule spends, on the average, from 6 h to 9 h and 45 min in the whole organism; 30-50% of this period is accounted for by residence in the central compartment. The volume of the central compartment reaches 208 mL/kg BW, and the MCR is estimated at 1.18 mL/min.kg BW for a steady state of 1 ng/mL plasma. The plasma dynamics of [D-Trp6,Des-Gly-NH2(10)]GnRH ethylamide in men are at least 10 times slower than those reported for the natural GnRH, thus indicating the relevance of its clinical use in suppressive therapy of LH secretion.
Adult↗
Regulation of mRNA expression of 3 beta-hydroxy-5-ene steroid dehydrogenase in porcine granulosa cells in culture: a role for the protein kinase-C pathway.
We studied the effect of the tumor-promoting phorbol ester phorbol 12-myristate 13-acetate (PMA), which activates protein kinase-C, on porcine granulosa cells in culture. PMA as well as cholera toxin, forskolin, and hCG increased cAMP accumulation. PMA further augmented the elevation in cAMP accumulation induced by cholera toxin, forskolin, and hCG. In the same cell culture model, hCG induced a time-dependent increase in the 3 beta-hydroxy-5-ene steroid dehydrogenase (3 beta HSD) mRNA levels with a maximal 3-fold stimulation obtained at 8-16 h of incubation with 1 IU hCG/ml. PMA inhibited the increase in 3 beta HSD mRNA levels induced by hCG in a dose-dependent manner. The phorbol ester also inhibited the increase in 3 beta HSD mRNA levels stimulated by LH as well as cholera toxin and forskolin and the cAMP analogs (Bu)2cAMP and 8-bromo-cAMP. Activation of protein kinase-C by mezerein similarly inhibited hCG stimulation of 3 beta HSD mRNA levels. The present data indicate that activation of the protein kinase-C pathway induces generation of cAMP, but causes a near-complete inhibition of the stimulatory effects of hCG, LH, forskolin, cholera toxin, and cAMP analogs on 3 beta HSD mRNA levels in porcine granulosa cells in culture.
3-Hydroxysteroid Dehydrogenases↗