PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “20-alpha-Hydroxysteroid Dehydrogenase”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1992

Expression of activities of two 20 alpha-hydroxysteroid dehydrogenase isozymes in rat corpora lutea.

The rat ovary contains two isozymes of 20 alpha-hydroxysteroid dehydrogenase (HSD-1 and HSD-2). In this study, the expression of activity of each isozyme was investigated in ovaries that contained a single generation of corpora lutea during pseudopregnancy. This condition was induced by cervical stimulation in rats that had been rendered anovulatory by housing them in a continuously lit environment. The total activity of cytosolic 20 alpha-HSD was lower in the ovaries of these pseudopregnant rats than in ovaries containing multiple generations of corpora lutea. In normal pseudopregnancy, HSD-1 activity was low on days 5 and 9 and increased markedly on day 15, whereas HSD-2 was lower than HSD-1 and did not vary throughout pseudopregnancy. However, on days 5 and 9 of continuous-light pseudopregnancy, low activity of HSD-1 only was detected; by day 15, HSD-1 activity had increased sixfold and HSD-2 activity could be detected. Immunohistochemical methods using a specific antibody recognizing both HSD-1 and HSD-2 revealed that the number of 20 alpha-HSD-positive luteal cells increased by day 15. Thus, the increase in total enzyme activity and appearance of HSD-2 activity observed at late pseudopregnancy was accompanied by an increase in the number of 20 alpha-HSD-positive luteal cells.

20-Hydroxysteroid Dehydrogenases↗
PubMed1992

20-alpha-Hydroxysteroid dehydrogenase from pseudopregnant rat ovary: obtention and characterization of a monoclonal antibody against the enzyme activity.

The enzyme 20-alpha-hydroxysteroid dehydrogenase (20-alpha-HSD) was purified from pseudopregnant rat ovaries and used as antigen for the development of a monoclonal antibody by the hybridoma technique. Spleen cells of BALB/c mice immunized with purified 20-alpha-HSD were fused with SP2/0 mouse myeloma cells. Among the colonies of hybrid cells, one (designated mAb-HSD 11) was found to be secreting antibodies (IgM) able to inhibit 20-alpha-HSD activity. The antibody-secreting hybridome was amplified by ascitic fluid production and the monoclonal antibody purified by Bakerbond ABx procedure. Purified mAb-HSD 11 was able to inhibit 20-alpha-HSD activity in a dose-dependent manner. Studies of Michaelis constants of 20-alpha-HSD indicate that this monoclonal antibody increases the Km for 20-alpha-dihydroprogesterone and decreases the Vmax.

20-Hydroxysteroid Dehydrogenases↗
PubMed1992

Translation of rat ovarian mRNA to two 20 alpha-hydroxysteroid dehydrogenase isozymes in Xenopus oocytes.

20 alpha-Hydroxysteroid dehydrogenase (20 alpha-HSD) in rat luteal tissue catalyzes the conversion of progesterone into a biologically inactive steroid, 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OHP) and depletes the output of progesterone into the circulation. An increase in 20 alpha-HSD activity in luteal tissue is therefore a prerequisite for the regression of functional corpora lutea in rats. We have reported that ovarian 20 alpha-HSD is composed of two isoforms (HSD1 and HSD2). In this study, among batches of ovaries collected randomly during the estrous cycle, we selected two batches (batches A and B): the cytosol preparation from batch A contained both HSD1 and HSD2 activities, whereas that from batch B contained only HSD1 activity. From these 2 batches, we extracted mRNA, and each mRNA preparation was subjected to translation in Xenopus oocytes. The translation products of batch A exhibited both HSD1 and HSD2 activities, and those of batch B only HSD1 activity in accordance with the enzymatic activities observed in the respective cytosolic preparations. The results are compatible with the presence of two distinct mRNAs coding HSD1 and HSD2, and if so their transcription will be regulated separately according to the functional state of the ovary.

20-Hydroxysteroid Dehydrogenases↗
PubMed1979

Effect of human chorionic gonadotropin and prolactin on 20 alpha-hydroxysteroid dehydrogenase activity in granulosa cells of immature rat ovary.

The effects of FSH, hCG, and PRL on the activity of 20 alpha-hydroxysteroid dehydrogenase (20 alpha-SDH) of separate ovarian components of hypophysectomized, diethylstilbestrol-treated rats were studied. Enzyme activity was found to reside mainly in granulosa cells. FSH induced an increase in enzyme activity. A preparation of FSH was purified by adsorbing its LH contamination on rat corpora lutea membranes and by further neutralizing LH traces with an antiserum to the beta-subunit of LH. This purified FSH retained the ability to induce a 6-fold increase in specific enzyme activity in granulosa cells of hypophysectomized, diethylstilbestrol-treated rats. Administration of hCG to rats treated with purified FSH, further enhanced 20 alpha-SDH activity in granulosa cells up to 11.5-fold above control. PRL, which is known to inhibit 20 alpha-SDH activity in regressing rat corpora lutea, suppressed the FSH-induced increase in enzyme activity in the granulosa cells.

20-Hydroxysteroid Dehydrogenases↗
PubMed1977

Suppression of 20 alpha-hydroxysteroid dehydrogenase activity in cultured rat luteal cells by prolactin.

20alpha-Hydroxysteroid dehydrogenase (20 alpha-SDH) activity increases in the cycling corpus luteum of the rat, beginning at 14.00 h on the day of diestrus, but remains low in corpora lutea of pregnancy throughout the first 19 days of gestation. When cells derived from 7-day-old corpora lutea of pregnant rats were cultured for 7 or 12 days, there was a spontaneous rise in 20 alpha-SDH activity from an initial value of 0.44 +/- 0.27 to 4.1 +/- 0.7 units/mg supernatant protein. Addition of LH (NIH-S-18; 2.0 mug/ml) or prostaglandin F2alpha (2.8 X 10(-5) M) to the medium from day 4 to the end of incubation period caused a slight but significant reduction in 20 alpha-SDH activity (20%, P less than 0.05). Supplementation of the medium with ovine prolactin (HIH-P-S11; 10.0 mug/ml) from the time of seeding or from the 2nd to 4th day of culture reduced the activity of 20 alpha-SDH measured on day 12 by 61% (P less than 0.001). This finding suggests that the suppression of 20 alpha-SDH by prolactin, hitherto demonstrated only in vivo results from a direct action of the hormone on the luteal cell.

Animals↗
PubMed1979

Effect of prostaglandin F-2 alpha on ovarian enzyme activity in the hysterectomized guinea-pig.

The enzymes studied were cholesterol esterase, cholesterol ester synthetase 3 beta-hydroxysteroid dehydrogenase and 20 alpha-hydroxysteroid dehydrogenase. PGF-2 alpha reduced the activities of 3 beta-hydroxysteroid dehydrogenase and cholesterol esterase but did not affect those of cholesterol ester synthetase of 20 alpha-hydroxysteroid dehydrogenase.

20-Hydroxysteroid Dehydrogenases↗
PubMed1978

Steroid metabolism in normal mammary gland and in the dimethylbenzanthracene-induced mammary tumor of rats.

After incubation of [4-14C]progesterone with cell-free homogenates of 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced mammary tumor of rats, 20 alpha-hydroxy-4-pregnen-3-one, 5 alpha-pregnane-3,20-dione, 20 alpha-hydroxy-5 alpha-pregnan-3-one, 3 alpha-hydroxy-5 alpha-pregnan-20-one, and 5 alpha-pregnane-3 alpha, 20 alpha-diol were identified as the metabolites. In normal mammary tissue, however, 4-pregnene-3 alpha-diol was isolated in addition to 5 alpha-reduced, and 3 alpha- and 20 alpha-hydroxy metabolites. When radioactive testosterone was employed as a substrate, 5 alpha-dihydrotestosterone and 5 alpha-androstane-3 alpha, 17 beta-diol were obtained as the metabolites of the mammary tumor. In the normal mammary gland, only 4-andorstene 3 alpha, 17 beta-diol was formed as its metabolite. Although the enzyme activities relevant to the metabolism varied among the tumor examined, the activity of 20 alpha-hydroxysteroid dehydrogenase in the mammary tumor was significantly lower than that in the normal mammary gland, whereas the activity of 5 alpha-reductase was higher in some of the mammary tumors than in the normal gland. The 5 alpha-reductase activity in the normal mammary gland was mostly localized in the crude microsomal fraction, whereas the same enzyme activity in the tumor was detected in all the organelle fractions. The activities of 20 alpha-hydroxysteroid dehydrogenase and NADPH-linked 3 alpha-hydroxysteroid dehydrogenase were found mainly in the cytosol fractions of the tumor and the normal tissue. The NADH-linked 3 alpha-hydroxysteroid dehydrogenase activity was detected only in the cytosol fraction of the normal mammary gland, but in the tumor studied, the activity of this enzyme was detected in all the subcellular fractions examined.

20-Hydroxysteroid Dehydrogenases↗
PubMed1976

Luteotropic regulation of dispersed rat luteal cells in early pregnancy.

Viable and functional luteal cells were prepared, using a combination of hyaluronidase, collagenase, and a low concentration of trypsin in a Dulbecco's modified Eagle medium containing 0.5% bovine serum albumin and 3.3 mM Ca++, from corpora lutea taken from 2-day pregnant rats. The viability and functional capacity of the dispersed cells were evaluated by electronmicroscopy and by measuring steroidogenic capicity during perifusion. Dispersed luteal cells previously exposed in vivo to biphasic prolactin (PRL) surges were found to respond during perifusion to as little as 0.5 ng/ml LH by increased steroid secretion. The net progesterone synthesis and secretion remained elevated over a time course of 2 1/2 hours perifusion, and the magnitude of the luteotropic stimulation was dose dependent on LH. However, luteotropic stimulation of LH could not be maintained beyond 2 1/2 h without renewed (in vitro) PRL exposure. PRL by itself maintained the low initial secretion rate of progesterone but demonstrated no stimulatory effect. Different steroidogenic responses were noted during the in vitro administration of LH alone and the administration of LH plus PRL. In the former case, the decreasing rate of progesterone secretion was accompanied by an increasing 20 alpha-dihydroprogesterone secretion, suggesting that luteal 20 alpha-hydroxysteroid dehydrogenase activity was not suppressed. In the latter case, progesterone secretion was maintained and 20 alpha-dihydroprogesterone secretion fell suggesting an inhibitory action by PRL against 20 alpha-hydroxysteroid dehydrogenase activity. Dispersed luteal cells, preincubated at 36 C in medium containing only PRL, retained viability and functional capacity in response to LH-PRL stimulation for periods of time up to 48 h. Preincubation with LH alone did not prolong cell viability.

20-alpha-Dihydroprogesterone↗
PubMed1976

Progesterone metabolism by the ovary of the pregnant rat: discrepancies in the catabolic regulation model.

The intraovarian site of 20 alpha-hydroxysteroid dehydrogenase activity (20 alpha-OH-SDH) was determined biochemically by measuring enzyme activity in homogenates of the whole ovary, or of isolated ovarian compartments, during the last third segment of pregnancy in the rat. In agreement, with previously reported histochemical evidence, an increase in 20 alpha-OH-SDH activity was observed in isolated corpora lutea, but not in the non-luteal compartment of the ovary. Enzyme activity in corpora lutea was low between days 16 and 22 of pregnancy, but increased markedly (4-6 fold) on day 23. Between days 17 and 20 of pregnancy, serum concentrations of progesterone declined from 130 +/- 3 to 80 +/- 3 ng/ml, while 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OH-P) concentrations declined from 34 +/- 3 to 18.5 +/- 3 ng/ml. Only later, between days 20 and 22 of pregnancy, was a significant decline in serum progesterone concentrations associated with an increase in serum 20 alpha-OH-P concentrations (50 +/- 15 ng/ml at 0800 h and 128.5 +/- 15 ng/ml at 1400 h on day 22). Thus the decline in progesterone concentration late in pregnancy can be explained only partially by conversion of progesterone to 20 alpha-OH-P. Further, a dissociation between changes in enzyme activity and in serum concentrations of 20 alpha-OH-P was also observed. A marked increase in serum levels of 20 alpha-OH-P on day 22 preceded any increase in enzyme activity by at least 10 h, and continued increases in enzyme activity on day 23 were not associated with any steady increase in peripheral 20 alpha-OH-P levels. We conclude from these observations that luteal regression is a more complex phenomenon than the regulation of a single enzyme, 20 alpha-hydroxysteroid dehydrogenase, and may involve regulation of both the synthesis and degradation of progesterone.

20-alpha-Dihydroprogesterone↗
PubMed1978

Control of placental 3 beta-hydroxy-delta 5-steroid dehydrogenase: an apparent endogenous regulator of porgesterone synthesis.

Dilution of tissue fractions from human placenta resulted in an increase in the specific activites of 3 beta-hydroxy-delta 5-steroid dehydrongease and of 20 alpha-hydroxysteroid dehydrogenase. The apparent Ks and V max of 3 beta-hydroxy-delta 5-steroid dehydrogenase were altered. It is postulated that this dilution effect is caused by the presence in the placenta of an endogenous inhibitor of steroid synthesis which may be important in the regulation of steroid output by this organ. A mathematical model of such an inhibitor corresponds well to the experimental results.

20-Hydroxysteroid Dehydrogenases↗
PubMed1978

Progesterone metabolism in cultured amniotic fluid cells.

Amniotic fluid cells obtained by amnicentesis at 16-20 weeks' gestation were grown in culture until a confluent monolayer of cell had been formed. Radiolabeled pregnenolone, progesterone and 20 alpha-dihydroprogesterone were added to the cell cultures; steroid metabolites which formed after 24 and 48 hours of incubation were identified. Incubation of the cell cultures with pregnenolone-3H resulted in the formation of progesterone, 17alpha-progesterone and 20 alpha-dihydroprogesterone. A significant amount of progesterone was identified after incubating the cell cultures with 20 alpha-dihydroprogesterone. The results indicate that 3 beta-ol-dehydrogenase, 17 alpha-hydroxylase and 20 alpha-hydroxysteroid dehydrogenase enzymes are present in cultured amniotic fluid cells obtained at 16-20 weeks' gestation.

20-alpha-Dihydroprogesterone↗
PubMed1979

Enzymes of steroid hormone metabolism in ovarian tissue of teleosts.

1. Substrate-velocity kinetics and some other characteristics of three enzymes involved in steroid hormone metabolism in the ovary of the common carp, Cyprinus carpio and of the grey mullet, Mugil cephalus were determined. 2. Labeled steroid products of the enzyme reactions were identified by thin-layer and gas-liquid chromatographies, as well as by formation of derivatives. 3. 5 alpha-Steroid reductase of carp ovary was found to have a Michaelis-Menten constant undistinguishable from that of rat ovarian tissue, while the Km of the enzyme in mullet ovarian tissue was found to be different. 4. The Km of 20 alpha-hydroxysteroid dehydrogenase of mullet ovarian tissue was similar to the value reported for mammalian gonadal tissue, but the constant for 17 beta-hydroxy-steroid dehydrogenase in the carp ovary was different. 5. It is for the first time that these enzymes of steroid hormone metabolism have been quantitatively determined in teleost ovarian tissue.

17-Hydroxysteroid Dehydrogenases↗
PubMed1979

Functional luteolysis in the pseudopregnant rat: effects of prostaglandin F2 alpha and 16-aryloxy prostaglandin F2 alpha in vitro.

The present work concerns the luteolytic effects of prostaglandin (PG) F2 alpha and its analogue, 16-aryloxy PGF2 alpha, upon isolated luteal cells. Varying doses of these two prostaglandins were incubated with cells in the presence or absence of an optimum stimulatory dose of LH (1 microgram/ml). The total contents of progesterone and 20 alpha-dihydroprogesterone in flasks were determined after the incubation periods by radioimmunoassay. Both prostaglandins inhibited basal synthesis of progesterone and 20 alpha-dihydroprogesterone, maximum inhibition occurring at concentrations of either PG of between 250 and 500 ng/ml. In this dose range both prostaglandins were found to abolish LH-stimulated progestogen synthesis completely. These effects were discernible within 5 min of incubation. The studies demonstrated that the onset of PG-induced luteolysis in vitro is characterized by an inhibition of the biosynthesis of both progesterone and its weakly progestogenic metabolite, 20 alpha-dihydroprogesterone; induction of 20 alpha-hydroxysteroid dehydrogenase activity by either PG was not found in incubations extending up to 60 min. In contrast to their relative potencies in vivo, PGF2 alpha and 16-aryloxy PGF2 alpha were essentially equipotent in this in-vitro system.

20-alpha-Dihydroprogesterone↗
PubMed1992

[Effect of gonadotropin releasing hormone agonist (Gn-RHa) on steroidogenesis in human and rat ovaries].

The effects of Gn-RHa on rat granulosa cells and on human granulosa and luteal cells were examined. (I) In rat granulosa cells: 1) Gn-RHa inhibited the stimulating effect of PMSG on progesterone and estradiol production. 2) In a tracer experiment, Gn-RHa inhibited PMSG-stimulated progesterone production by stimulating 20 alpha-hydroxyprogesterone production. On the other hand, Gn-RHa inhibited estradiol production by inhibiting PMSG-stimulated aromatization. 3) On 20 alpha-hydroxysteroid dehydrogenase activity, it appears that Gn-RHa accelerates the maximum velocity and decreases the affinity of the enzyme to 20 alpha-hydroxyprogesterone as the substrate. (II) In man: 1) In granulosa cells during the ovulatory phase, Gn-RHa inhibited PMSG-stimulated progesterone and estradiol production. 2) In luteal cells, Gn-RHa inhibited hCG-stimulated progesterone production. 3) The affinity of Gn-RH receptor in the corpus luteum was lower than that in rat ovaries. These results suggest that in the human ovary as well as in the rat ovary, Gn-RHa might have a direct effect on the development of the follicle.

Animals↗
PubMed1979

20 alpha-Hydroxysteroid oxidoreductase activity and 20 alpha-dihydroprogesterone concentration in human placenta before and after parturition.

The objective of this investigation was to determine if decreased biosynthesis or increased catabolism of progesterone (P) during labor was responsible for the decreased concentration of hormone observed in the human placenta after labor and vaginal delivery. No significant difference was found in P biosynthesis by placental tissues examined before and after labor as evidenced by a similar activity of 3 beta-hydroxysteroid dehydrogenase: delta 5-isomerase. In contrast, there was a marked increase in P catabolism during labor, as shown by a significant (p less than 0.05) change in placental 20 alpha-hydroxysteroid oxidoreductase activity which increased from 835.5 +/- 103 (mean +/- SEM) pmoles of 20 alpha-dihydroprogesterone (20 alpha-DHP) generated per milligram of protein per hour before labor to 1,160.4 +/- 101 pmoles/mg/hr after labor. A similar significant (p less than 0.02) increase in enzyme activity was noticed in parallel assays of the reverse (20 alpha-DHP leads to P) reaction. As a consequence of increased P catabolism, placentas after labor had a 20 alpha-DHP concentration of 63.7 +/- 9.5 (mean +/- SEM) ng/mg protein, a value which was significantly (p less than 0.05) larger than that found before labor (37.8 +/- 8.3 ng/mg protein). These changes resulted in a modification of the placental tissue P/20 alpha-DHP ratio which decreased from 2/1 before to 1/1 after labor. The results indicate that the catabolism of P to 20 alpha-DHP increases significantly during human parturition. This phenomenon may be of importance in the mechanism of initiation and continuation of labor.

20-Hydroxysteroid Dehydrogenases↗
PubMed1979

Metabolism of progesterone by placentas from several mammalian species in vitro.

20-alpha-Hydroxysteroid oxidoreductase (20-alpha-HSDH) activity and 20-alpha-dihydroprogesterone concentration (20-alpha-DHP) reach peak values in the human placenta after vaginal delivery. To determine if these findings are unique to the human, we measured 20-alpha-HSDH activity as well as endogenous progesterone (P) and 20-alpha-DHP concentration in the soluble supernatant fraction of placental tissues obtained from rodents (rat, rabbit, guinea pig), ungulates (horse, zebra, giraffe, cow), and primates (squirrel monkey, orangutan, man). P concentration was very low in rodents (mean 0.60 ng/mg protein), increased slightly in ungulates (mean 2.89 ng/mg protein), and reached a maximum value in the human (34.43 ng/mg protein). 20-alpha-DHP concentration had a strong positive correlation (r = 0.93) with P tissue content; it was low in rodents (mean 0.21 ng/mg protein), increased slightly in ungulates (mean 0.79 ng/mg protein), and reached a maximum value in the human (39.53 ng/mg protein). 20-alpha-HSDH activity, however, had a poor correlation with 20-alpha-DHP tissue concentrations: Its lowest value was in the guinea pig (9.34 pmole/mg protein/hour) and the highest was in the horse (3.19 nmole/mg protein/hour). These results indicate that a high level of activity of the P to 20-alpha-DHP pathway with significant tissue accumulation of 20-alpha-DHP is unique to the human placenta and reinforce the possibility of its causing in situ P withdrawal as a part of the overall mechanism of human parturition.

20-alpha-Dihydroprogesterone↗