Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0338671 (Steroids)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A direct method for determination of delta 5 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity was employed in isolated Leydig cells (LC) derived from rats on fetal day 19 (Fig) and postnatal (N) days 1, 12, 24, 34 and 45 and adults. The activity of 3 beta-HSD in the adult LC was 1.15 +/- 0.02 (mumole/microgram DNA/hr, mean +/- SEM, n = 73). Activities in the other groups, expressed as a percentage of the respective adult control, were: Fig-38%; N1-39%; N12-8%; N24-89%; N34-166%; and N45-118%. A good correlation was found between histochemical staining for 3 beta-HSD and the quantitive method employed. Using (3H)-DHA as a substrate, LC isolated from F19, N1 and N12 produced testosterone in appreciable amounts (41%, 55% and 20% of the total products respectively) whereas at advanced stages of development (N24 to adulthood) the major product was androstenedione (93 +/- 1%). These findings may be explained by the observed decrease in 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity, due to an insufficient supply of NADPH, in the older vs. earlier stages of development. This study indicates the presence of steroidogenic enzymatic activity in LC throughout development in the rat. It also provides a relatively simple in vitro model for studies of testicular regulation during development.
Steroids 1980 Dec
PMID:Developmental pattern of delta 5 3 beta-hydroxysteroid dehydrogenase activity in isolated rat Leydig cells. 693 86

NADPH-dependent 20 alpha-hydroxysteroid oxidoreductase (20 alpha-HSD; EC 1.1.1.149) from bovine fetal erythrocytes was obtained for the first time free of hemoglobin by a new 2,500-fold purification scheme. This was achieved by a sequence of calcium phosphate gel absorption, ammonium sulfate fractionation, and affinity chromatography. The present results lead us to believe that the NADPH-dependent 3 beta-hydroxysteroid oxidoreductase activity, which was co-purified with 20 alpha-activity, may originate at the active site of 20 alpha-HSD (2).
Steroids 1981 May
PMID:Purification of 20 alpha-hydroxysteroid oxidoreductase from bovine fetal erythrocytes. 694 32

Human placental estradiol 17 beta-dehydrogenase (E.C. 1.1.1.62) was inactivated at pH 6.3 by 3-bromo [2'-14C] acetoxy-1,3,5(10) estratrien-17-one, a know substrate. The affinity-alkylated enzyme was then hydrolyzed by trypsin. Radioactive peptides were initially isolated by gel filtration and identified according to which residue was alkylated. Tryptic peptides containing radioactive 3-carboxymethylhistidyl residues were further purified by cation-exchange chromatography. The population of these peptides varied, depending upon the conditions of enzyme inactivation. With 60 microM 3-bromo[2'-14]acetoxy-1,3,5 (10) estratrien -17-one four major peptides (a,b,c,d) each containing radioactive 3-carboxymethylhistidine, were eluted from the cation-exchange column. The alkylation of all of these peptides was completely suppressed when the enzyme was inactivated in the presence of excess estradiol-17 beta. The presence of equimolar NADPH during incubation greatly enhanced the alkylation of all four peptides. In the presence of NADPH, estradiol-17 beta most significantly decreased the formation of peptide d. Peptide d was the only peptide identified when the concentration of the alkylating steroid was lowered to 6 microM, a value approaching the Km. These observations indicate that peptide d is a histidyl-bearing peptide from the steroid-binding site which proximates the steroid A-ring. They further suggest that with the affinity labeling steroid at higher concentrations other nonspecific, hydrophobic sites on the enzyme are occupied and labeled.
Steroids 1982 Feb
PMID:Isolation of histidyl peptides of the steroid-binding site of human placental estradiol 17 beta-dehydrogenase. 695 20

C17-20Lyase and 21-hydroxylase activities were measured during late gestation in the rhesus monkey (Macaca mulatta) fetal adrenal. Activities were assessed in 10,000 x g supernatants with 17-hydroxyprogesterone and NADPH as substrates. Although conversion of [14C]17-hydroxyprogesterone to [14C]androstenedione was noted, activity was often nonlinear and far less than the rate of hydroxylation which together prevented an accurate estimation of lyase rate, Km and Vmax. 21-Hydroxylase activity was characterized; the mean reaction rate was 1.6 x 10(-3) mumoles NADPH oxidized/min. x mg-1 protein with an apparent Km of 3.6 x 10(-7) M and a Vmax of 2.2 x 10(-3) mumoles/min. x mg-1 protein. These values were similar to data obtained in adrenals from adult monkeys. A relatively high level of hydroxylase activity in the fetal gland might lead to an inadequate supply of precursors for the synthesis of dehydroepiandrosterone sulfate (DHEAS) in the adrenal if it also contained 3 beta-hydroxysteroid dehydrogenase (3 beta-hsdh). However, the fact that the fetal adrenal reportedly is deficient in 3 beta-hsdh may serve to protect both DHEAS and corticoid synthesis.
Steroids 1981 Aug
PMID:17-Hydroxyprogesterone metabolism in the monkey fetal adrenal: C17-20lyase and 21-hydroxylase activities. 697 10

There is indirect evidence that cortisol synthesis in the fetal rhesus monkey adrenal gland is limited at Day 135 of gestation but increases thereafter. This study was conducted to ascertain whether a reduced synthetic capacity is caused by a deficiency in 17-, 21- or 11-hydroxylase activity. For the sake of comparison 11- and 21-hydroxylases were also estimated in adult adrenals. 11-, 21-Hydroxylases were measured in the entire adrenal by the oxidation of NADPH by mitochondria and microsomes, respectively. 17-Hydroxylase was evaluated in outer and inner regions of the fetal gland by the formation of [3H]17-hydroxyprogesterone, -11-deoxycortisol, -cortisol and -androstenedione from [3H]progesterone. The maximum velocity of both the 11- and 21-hydroxylase was similar in fetal and adult glands indicating that corticoid formation in the fetus is not constrained by levels of these enzymes. [3H]Progesterone was extensively metabolized to -17-hydroxyprogesterone, -androstenedione, -11-deoxycortisol and -cortisol by homogenates from both regions of the fetal adrenal. The ratio of [3H]-cortisol to [3H]11-deoxycortisol was consistently higher in incubations of the inner glandular area. Together, these findings indicate that 17-hydroxylase is also active at Day 135 and that the 11-hydroxylase may be more concentrated in the fetal cortex. These data suggest in addition that the restriction in cortisol formation occurs at a step prior to the metabolism of progesterone to cortisol.
Steroids 1982 Oct
PMID:Corticoid formation by the monkey fetal adrenal: evaluation of 17-, 21-, and 11-hydroxylase activities. 717 Jul 54

The ability of bovine liver and fat to metabolize progesterone and also to form glucuronide conjugates with these progestins in vitro was investigated. Tissue supernatants were incubated with [4-14C] progesterone, UDP-glucuronic acid, and a NADPH generating system for 5 hr, at 37 degrees C. Steroids were identified by thin-layer chromatography, high performance liquid chromatography, and recrystallization to a constant specific activity. The total original radioactivity which could not be removed by exhaustive ether extraction (presumptive conjugates) was 44.7 +/- 14.2% in liver, 5.0 +/- 3.6% in subcutaneous fat, and 3.7 +/- 2.2% in kidney fat samples. Progestins identified in liver samples include 5 beta-pregnane-3 alpha, 20 alpha-diol (free and conjugate), 5 beta-pregnane-3 alpha, 20 beta-diol (free and conjugate), 3 alpha-hydroxy-5 beta-pregnan-20-one (free and conjugate), 3 beta-hydroxy-5 beta-pregnan-20-one (free), 5 beta-pregnane-3,20-dione (free), and progesterone (conjugate). Progestins identified in both the free and conjugate fractions of subcutaneous fat and kidney fat samples include progesterone, 3 alpha-hydroxy-5 beta-pregnan-20-one, 20 beta-hydroxy-4-pregnen-3-one, and 20 alpha-hydroxy-4-pregnen-3-one. Differences due to sex of bovine used were noted. These results confirm the ability of bovine liver to readily metabolize progesterone and form glucuronide conjugates of these compounds and suggest that adipose tissues take an active role in these actions in cattle.
Steroids 1982 Sep
PMID:Metabolism and conjugation of [4-14C]progesterone by bovine liver and adipose tissues, in vitro. 718 4

Some derivatives of 6-methylene-4-pregnen-3-one were studied as inhibitors of delta 4-3-ketosteroid 5 alpha-reductase. Maximum inhibitory activity was shown by 17-acetoxy-6-methylene-4-pregnene-3,20-dione (AMPD). Irreversible inactivation was observed following preincubation of the enzyme with NADPH and AMPD. This inactivation was found to occur only in the presence of NADPH. As such enzyme inactivation was not due to the formation of a more inhibitory metabolic product, or to the formation of superoxide via a cytochrome P-450/NADPH pathway, it seemed likely that the observed inactivation was derived from an irreversible combination of the enzyme with AMPD. That this was probably the case was established by kinetic studies which revealed a pattern compatible with a kcat type of mechanism.
Steroids 1981 Aug
PMID:Prostatic cancer. I. 6-Methylene-4-pregnen-3-ones as irreversible inhibitors of rat prostatic delta 4-3 ketosteroid 5 alpha-reductase. 730 26

Suitable incubation conditions were developed for reduced pyridine nucleotide protection and regeneration to permit quantitative assessment of the NADPH requirement for steroid aromatization by human placental microsomes. 10 mM dithiothreitol was found to protect NADP(H) from microsomal nucleotide pyrophosphatase and 2 mM nicotinamide mononucleotide was utilized to control nucleotide glycohydrolase activity. Under these assay conditions, the initial rates of aromatization obtained with restricted NADPH levels were critically dependent upon both the amount and the source of exogenous NADPH-regenerating dehydrogenase system. With excess Leuconostoc mesenteroides glucose-6-phosphate dehydrogenase, an apparent Km for NADPH of 0.20 microM was observed for aromatization which is significantly below all previous estimates of the NADPH requirement and which is at greatest only one-tenth the Km value for NADPH utilization by NADPH-cytochrome c reductase. These findings suggest a potential regulatory role for both NADPH-generating and NADPH-accepting enzymes in the support of estrogen biosynthesis.
Steroids 1981 Aug
PMID:Quantitative requirements for NADPH in the support of aromatization by human placental microsomes. 730 32

This study has identified the polar metabolites of 5 alpha-androstane-3 beta-17 beta-diol(3 beta-diol) produced by the canine prostate. The major metabolite is 5 alpha-androstane-3 beta,7 alpha,17 beta-triol(7 alpha-triol) accounting for approximately 80% of the total polar metabolites of 3 beta-diol. The remaining 20% is accounted for exclusively by another triol, 5 alpha-androstane-3 beta,6 alpha,17 beta-triol(6 alpha-triol). This study has also characterized two enzymatic hydroxylase responsible for respective triol formation: 5 alpha-androstane-3 beta,17 beta-diol 6 alpha-hydroxylase(6 alpha-hydroxylase) and 5 alpha-androstane-3 beta,17 beta-diol 7 alpha-hydroxylase(7 alpha-hydroxylase). Both of these irreversible hydroxylases are located in the particulate fraction of the prostate and can utilize either NADH or NADPH as cofactor. Several in vitro steroid inhibitors of these hydroxylases were identified including cholesterol, estradiol and diethylstilbestrol. Neither of the hydroxylases were found to be decreased by castration (3 months) when expressed as activity/DNA. Using a variety of C19 androstane substrates, 6 alpha- and 7 alpha-triol were found to be major components of the total 3 beta-hydroxy-5 alpha-androstane metabolites produced by the canine prostate.
Steroids 1980 Feb
PMID:The identification and characterization of the C19O3 steroid metabolites of 5 alpha-androstane-3 beta,17 beta-diol produced by the canine prostate: 5 alpha-androstane-3 beta,6 alpha,17 beta-triol and 5 alpha-androstane-3 beta,7 alpha,17 beta-triol. 737 15

Adrenal gland homogenates from four different strains of mice were incubated with (4-14C)-pregnenolone and a NADPH generating system. Although quantitative differences between high and low mammary tumor strains occured, all mice synthesized estrone. The highest aromatase activity was found 2 months after castration of the (C3H x RIII) F1 mice when castration was performed at 4 days of age; this activity was lower in the C3H mice and almost negligible in the RIII and C57BL mice.
Steroids 1980 Apr
PMID:In vitro pregnenolone metabolism by mouse adrenal gland: I-estrogen synthesis. 737 27


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