Showing papers on "Steroid biosynthesis published in 1995"

Ligand-regulated site-specific recombination

Abstract: Site-specific recombination offers a potential way to alter a living genome by design in a precise and stable manner. This potential requires strategies which can be used to regulate the recombination event. We describe a strategy to regulate FLP recombinase activity which relies on expressing FLP as a fusion protein with steroid hormone receptor ligand binding domains (LBDs). In the absence of a ligand cognate to the LBD, the recombinase activity of the fusion protein is extremely low. Upon ligand administration, recombinase activity is rapidly induced. These results outline the basis for inducible expression or disruption strategies based on inducible recombination. Additionally, we have exploited the conditional nature of FLP-LBD fusion proteins to direct integration of a plasmid into a specific genomic site at frequencies approaching the frequency of random integration.

Interleukin-1α and -β modulation of luteinized human granulosa cell oestrogen and progesterone biosynthesis

Abstract: This study was designed to test the hypothesis that interleukin-1 alpha (IL-1 alpha) and beta directly affect progesterone, and oestradiol production in cultures of purified human granulosa cells. Luteinized granulosa cells were obtained from women during in-vitro fertilization cycles. Granulosa cells with and without associated white blood cells were cultured in the presence of IL-1 alpha and IL-1 beta (0.5-50 ng/ml) for 48 h. Media were changed at 24 h intervals and assayed for progesterone and oestradiol. In separate experiments, granulosa cell viability was assessed with the tetrazolium salt reduction assay, haemocytometer cell counts, and Trypan blue dye exclusion. Our results indicate that progesterone synthesis by basal and human chorionic gonadotrophin (HCG)-stimulated granulosa cells co-cultured with white blood cells was inhibited by 5.0 ng/ml of IL-1 alpha and IL-1 beta at 48 h of culture. In the presence of white blood cells, granulosa cell oestradiol synthesis was inhibited by IL-1 beta but not IL-1 alpha. Oestradiol was inhibited after both 24 and 48 h of culture and was maximally affected by 5.0 ng/ml of IL-1 beta. In contrast, basal and HCG-stimulated oestradiol production by granulosa cells cultured free of white blood cells was inhibited only by IL-1 alpha. IL-1 alpha at 5.0 ng/ml produced maximal inhibition of basal oestradiol (57%) and HCG-stimulated oestradiol (41%) production at 48 h of culture. Gonadal steroid inhibition by IL-1 alpha and IL-1 beta was not mediated through cytotoxic or antiproliferative effects on granulosa cells. Specificity of the granulosa cell response to IL-1 alpha and IL-1 beta was demonstrated by abrogation of steroid inhibition with anti-IL-1 alpha and IL-1 beta neutralizing antibodies. In conclusion, IL-1 alpha directly inhibited the production of oestradiol by human ovarian granulosa cells. IL-1 alpha and IL-1 beta also exerted indirect effects on steroid production via white blood cells that are usually present in granulosa cell cultures if steps are not taken to remove them. These data support the hypothesis that cytokines play an important role in intra-ovarian regulation of steroid biosynthesis.

Immunocytochemical analyses of dehydroepiandrosterone sulfotransferase in cultured human fetal adrenal cells.

Abstract: Dehydroepiandrosterone sulfate is the major steroid secretory product of the human fetal adrenal gland. Several factors have been shown to modulate the secretion of this steroid by cultured fetal adrenal cells. In addition to the cytochrome P450 enzymes that are important in steroid biosynthesis, dehydroepiandrosterone sulfotransferase (DST) is likely to be a key regulated enzyme in the formation of sulfated steroids, which are characteristic of the human adrenal cortex, particularly that of the fetus and the adult zona reticularis. In the present investigation, we sought to evaluate the cellular localization of DST in cultures derived from the fetal zone, neocortex, and adrenal capsule and to determine the effects of ACTH and other agonists of the protein kinase-A pathway on the abundance of DST in such cells. Cells derived from the fetal zone, neocortex, and adrenal capsule were either precultured for 3-13 days in plastic flasks followed by culture on coverslips or were cultured directly on coverslips i...

Phase I/II dose-escalation study of liarozole in patients with stage D, hormone-refractory carcinoma of the prostate.

Abstract: Background: Liarozole binds to the cytochrome P-450-dependent hydroxylating enzymes involved in steroid biosynthesis and retinoic acid catabolism. This phase I study investigated the clinical/endocrine toxicity profile of liarozole and determined the maximally tolerated dose (MTD) in hormone-refractory prostate cancer patients. Methods: Groups of five patients were treated with oral liarozole caplets, starting at 37.5 mg twice daily. The dose was doubled for each subsequent group until the MTD was reached, after which, an additional 18 patients were entered into the MTD-1 dose stratum. The long-term safety of liarozole was assessed based on treatment-emergent signs and symptoms and clinically significant laboratory results. Results: Thirty-eight patients were enrolled. The MTD was determined to be 300 mg twice daily. Side effects that defined the MTD included lethargy, somnolence, body rash, and paresthesias. Two deaths occurred during the trial (pneumonia and myocardial infarction). Four patients had a >50% decrease in prostate-specific antigen (PSA) levels (two at 150 mg, two at 300 mg). Of nine patients with measurable disease, two had partial responses. Conclusions: Liarozole was generally well tolerated with no evidence of adrenal insufficiency. Preliminary evidence of activity in this indication was observed based on dose-dependent decreases in PSA levels and improvement in soft-tissue metastasis.

Evidence for cardiovascular effects of prorenin.

Abstract: This report investigates whether there is evidence that prorenin has cardiovascular effects. The report concludes that prorenin may indeed have cardiovascular effects, causing regional vasodilation by counteracting the vasoconstrictor effect of renin, and thereby maintaining blood flow to vital organs. This view is based on several observations. In direct contrast to renin, high levels of prorenin are not associated with vasoconstriction. (1) Prorenin is expressed almost exclusively in tissues with extraordinarily high levels of blood flow: pregnant uterus, placenta, ovaries, kidneys, eyes. (2) In the ovaries, the higher the prorenin level the higher the level of steroid biosynthesis, consistent with a increased tissue perfusion or metabolism. (3) Blood pressure gradually falls when prorenin is infused into monkeys, even when the source of prorenin is contaminated with renin which should increase blood pressure. (4) Prorenin levels positively correlate with renal blood flow under several experimental conditions. (5) Salt sensitivity of blood pressure, a renal vasoconstricted state, is associated with subnormal prorenin levels. (6) Diabetes mellitus and pregnancy, two vasodilated states, are associated with high plasma prorenin levels. (7) Prorenin binds to a membrane receptor that also recognizes renin. Thus, prorenin could vasodilate by competing with the specific uptake of renin and thereby reduce the level of regional vasoconstriction. Altogether, the cardiovascular haemodynamic setting associated with high levels of prorenin is the opposite of that associated with high levels of renin and is consistent with a vasodilator effect in the kidneys and reproductive organs and perhaps elsewhere.

Induction of immediate early gene mRNAs and proteins by hCG in interstitial cells of rat testis.

Abstract: In the present study we have investigated the induction of immediate early gene (IEG) c-fos, c-jun, junB and junD mRNAs and proteins in interstitial cells of rat testis after hCG treatment in vivo using in situ hybridization and immunocytochemistry. The basal levels of all IEGs were barely detectable with our methods. A prominent induction of c-fos, c-jun and junB mRNAs and proteins in Leydig cells was seen after hCG treatment. The induction of these IEG mRNAs and proteins demonstrates that their expression is an early transcriptional response to the extracellular stimulus of hCG and that they are involved in transcriptional processes which may mediate the effects of LH on cellular adaptive responses or steroid biosynthesis.

Regulation of 11β-hydroxylase cytochrome P450 expression by cholesterol in spontaneously hypertensive rats

Abstract: OBJECTIVE To investigate whether hypercholesterolaemia interferes with the expression of the enzymes involved in steroid biosynthesis in the adrenal cortex. METHODS Twenty-four 5-week-old male spontaneously hypertensive rats (SHR) were randomly assigned to a high (1%) cholesterol diet (n = 8) or to a matched cholesterol-free diet (n = 8) for 6 weeks. A third group (n = 8) was studied after 2 weeks of washout from the high-cholesterol intake. A cohort of age- and sex-matched normotensive Wistar-Kyoto (WKY) rats (n = 24) underwent the same treatments and was used as a control. RESULTS In SHR cholesterol feeding reduced urinary sodium excretion (0.8 +/- 0.1 versus 1.4 +/- 0.1 mmol/24 h in the cholesterol-free group), increased plasma aldosterone levels (299 +/- 60 versus 154 +/- 24) and reduced plasma corticosterone levels (142 +/- 21 versus 278 +/- 35 ng/ml). Those responses were associated with a reduction of 11 beta-hydroxylase cytochrome P450 messenger RNA (mRNA) in the adrenal cortex (-52.3 +/- 3.4%) whereas aldosterone synthase mRNA remained unchanged. That effect and the changes in electrolyte excretion and steroid levels were no longer detectable after withdrawal of the diet. In WKY rats high-cholesterol diet induced no significant changes in urinary electrolyte excretion, steroid levels and expression of 11 beta-hydroxylase cytochrome P450 and aldosterone synthase in the adrenals. CONCLUSIONS The present results indicate that in SHR hypercholesterolaemia selectively interferes with the adrenal steroid biosynthetic pathway by reducing the expression of 11 beta-hydroxylase, leading to accumulation of mineralocorticoids and sodium retention.

Pregnenolone Metabolism in the Ovarian Thecal Layers of the Rainbow Trout, Oncorhynchus mykiss: in vitro Inhibitory Effects of Cyanoketone and Trilostane

Abstract: The effects of sperific inhibitors of cyanoketone and trilostane, on metabolism in isolated ovarian thecal layers have been investigated in vitro. At all doses of cyanoketone and trilostane enzyme activity that transforms pregnenolone to was inhibited in the thecal layers. Trilostane appeared to be more efficient than cyanoketone. Trilostane at doses of caused a dose-response inhibition of steroids accumulation in the medium from pregnenolone, but not completely blocked the conversion of steroids.

Effects of 3-[N-(2-chlorobenzyl)amino]-6-(1H-imidazol-1-yl) pyridazine dihydrochloride on various aromatase enzyme systems and experimental breast cancer.

Abstract: The effects of 3- [N- (2-chlorobenzyl ) amino ]-6- (1H-imidazol-1-yl)pyridazine dihydrochloride (CAS 124070-28-3, MFT-279) on various aromatase enzyme systems and experimental breast cancer were studied. MFT-279 inhibited the aromatase enzyme in vitro with an IC 50 value of 2.39 nmol/l. On the other hand, MFT-279 had no effect on cytochrome P-450 dependent reactions of steroid biosynthesis. In pregnant mares' serum gonadotropin (PMSG)-treated female rats, the elevation of ovarian aromatase activity was significantly suppressed by the oral treatment with MFT-279 at 10 and 20 mg/kg When MFT-279 (20 mg/kg) was orally given to 9,10-dimethyl-1,2-benzanthracene (DMBA)-treated female rats once a day for 28 days, regression of tumors was observed. These results suggest that MFT-279 may be useful for the endocrine therapy of hormone dependent mammary carcinoma.