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PubMed1976

Some enzymatic properties of 3beta-hydroxysteroid oxidase produced by Streptomyces violascens.

The 3beta-hydroxysteroid oxidase produced by Streptomyces violascens was purified from the culture broth by procedures including batch-wise treatment on DEAE-cellulose, ammonium sulfate fraction, gel filtration on Sephadex G-75, and column chromatography on DEAE-cellulose. The highly purified enzyme preparation exhibited no significant absorption maxima in the visible region other than a maximum at 280 nm. Optimum pH and temperature for the enzyme activity were approximately pH 7.5 and 50 degree, respectively. The Michaelis constant (Km) for cholesterol determined under two different experimental conditions were 4.5 and 6.7 X 10(-4) M. The enzymatic activity was remarkably inhibited by various metal salts such as FeC1(3), FeSO4, AgNO3, etc. On the other hand, neither EDTA nor Fe-chelating agents had any inhibitory effect on the enzymatic activity, while other metal-binding agents, KCN and NaN3, caused significant inhibition. The enzyme activity was inhibited almost completely by N-bromosuccinimide and iodine but not p-chloromercuribenzoate. The highly purified enzyme did not require any external electron acceptors other than oxygen. In addition, the activity was not influenced by the addition of external electron donors. The enzyme showed a high substrate specificity for 3beta-hydroxysteroids and the relative oxidation rates were 100 for cholesterol, 91 for 5alpha-cholestan-3beta-ol, 83 for pregn-5-en3beta-ol-one, 80 for androst-5-en-3beta-ol-17-one, 64 for 5alpha-androstan-3beta-ol-17-one, ect. The oxidation of cholesterol by the enzyme was remarkably inhibited by the addition of 5alpha-cholestan-3beta-ol, 5alpha-cholestan-3-one, 5beta-cholestan-3beta-ol, 5alpha-cholestane3beta, 5alpha-doil or 5alpha-lanosta-8, 24-den 3beta-ol. These findings indicate the present enzyme belongs to the class of 3beta-hydroxysteroid oxidase but some of its physical and enzymatic properties obviously differ from those of 3beta-hyroxysteroid oxidase of Brevibacterium.

Cholesterol↗
PubMed1993

Localization of 3 beta-hydroxysteroid dehydrogenase in the chicken ovarian follicle shifts from the theca layer to granulosa layer with follicular maturation.

3 beta-Hydroxysteroid dehydrogenase (3 beta-HSD) catalyzes the conversion of pregnenolone to progesterone in the delta 4-3-ketosteroid metabolic pathway and dehydroepiandrosterone to androstenedione in the delta 5-3 beta-hydroxysteroid pathway. It has been suggested that small follicles of the chicken ovary that have not entered the follicular hierarchy metabolize steroids via the delta 5-3 beta-hydroxysteroid pathway, whereas preovulatory follicles that have entered the hierarchy metabolize steroids via the delta 4-3-ketosteroid pathway. Our objective was to localize 3 beta-HSD in follicles of the chicken ovary by immunocytochemistry using an anti-human placental 3 beta-HSD polyclonal antiserum to identify steroidogenic cells that convert pregnenolone to progesterone and/or dehydroepiandrosterone to androstenedione. Three groups of follicles of different maturities were examined: small follicles (1-10 mm in diameter and that have not entered the hierarchy), preovulatory follicles (10-35 mm in diameter and that have entered the hierarchy), and the most recent postovulatory follicle. Chicken ovaries were obtained 2 h after oviposition and fixed with Bouin's solution. Tissues were dehydrated with a series of ethanol, embedded in Paraplast (Brunswick Company, St. Louis, MO), and sectioned. Sections (4 microns) were immunostained for 3 beta-HSD with a Rabbit ExtrAvidin Staining Kit (Sigma Chemical Co., St. Louis, MO). 3 beta-HSD was localized in the single theca layer of cortical follicles (approximately 1 mm in diameter), which are still embedded in the stromal tissue, and in the theca interna and externa of other small follicles (< 10 mm in diameter). No immunoreactivity was observed in the granulosa layer of the majority of small follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed2001

Dominant bovine ovarian follicular cysts express increased levels of messenger RNAs for luteinizing hormone receptor and 3 beta-hydroxysteroid dehydrogenase delta(4),delta(5) isomerase compared to normal dominant follicles.

The objective was to compare ovarian steroids and expression of mRNAs encoding cytochrome P450 side-chain cleavage, cytochrome P450 17 alpha-hydroxylase, cytochrome P450 aromatase, 3 beta-hydroxysteroid dehydrogenase Delta(4),Delta(5) isomerase, LH, and FSH receptors and estrogen receptor-beta in ovaries of cows with dominant and nondominant ovarian follicular cysts and in normal dominant follicles. Estradiol-17 beta, progesterone, and androstenedione concentrations were determined in follicular fluid using specific RIAs. Dominant cysts were larger than young cysts or dominant follicles, whereas nondominant cysts were intermediate. Estradiol-17 beta (ng/ml) and total steroids (ng/follicle) were higher in dominant cysts than in dominant follicles. Expression of LH receptor and 3 beta-hydroxysteroid dehydrogenase mRNAs was higher in granulosa cells of dominant cysts than in dominant follicles. Nondominant cysts had higher follicular concentrations of progesterone, lower estradiol-17 beta concentrations, and lower expression of steroidogenic enzyme, gonadotropin receptor, and estrogen receptor-beta mRNAs than other groups. In summary, increased expression of LH receptor and 3 beta-hydroxysteroid dehydrogenase mRNAs in granulosa and increased follicular estradiol-17 beta concentrations were associated with dominant cysts compared to dominant follicles. Study of cysts at known developmental stages is useful in identifying alterations in follicular steroidogenesis.

3-Hydroxysteroid Dehydrogenases↗
PubMed1975

3Alpha-hydroxysteroid dehydrogenase from Pseudomonas testosteroni: kinetic properties with NAD and its thionicotinamide analogue.

The kinetics of 3alpha-hydroxysteroid : NAD oxidoreductase (EC 1.1.1.50) from Pseudomonas testosteroni (ATCC 11996) have been investigated. The kinetic analysis based on initial activity measurements and product inhibition studies, indicates that the addition of substrate to the enzyme and the release of products from it, follows an obligatory order (ordered bi bi mechanism). The ability of the enzyme to utilize the thionicotinamide analogue of NAD (sNAD) as cofactor has been investigated using various 3alpha-hydroxysteroids from both the C19, C21, and C24 series. The results show that the reaction velocity with sNAD as the cofactor is generally lower than with NAD. The decrease, however, varies considerably, being negligible with some steroids such as litocholic acid and deoxycholic acid and very pronounced with other such as tetrahydrocortisol and tetrahydrocortisone. The introduction of an 11beta-hydroxy or an 11-oxo group into the steroid molecule significantly reduces the ability of the enzyme to attack the 3alpha-hydroxy group. No such effect could be seen when the 11-hydroxy group was in the alpha-position. The results also indicate that, whereas NAD can serve as cofactor for both the monomeric and the dimeric forms of the enzyme, sNAD only acts as cofactor for the monomeric form. Thus sNAD is a valuable tool for the study of the reversible, concentration-depenedent monomeric-dimeric transition of the 3alpha-hydroxysteroid dehydrogenase.

Androstanes↗
PubMed1989

Partial purification and characterization of an NAD-dependent 3 beta-hydroxysteroid dehydrogenase from Clostridium innocuum.

In nine strains of Clostridium innocuum, 3 beta-hydroxysteroid-dehydrogenating activities were detected. 3 beta, 7 alpha, 12 alpha-Trihydroxy- and 3 beta-hydroxy-12-keto-5 beta-cholanoic acids were identified as reduction products of the respective 3-keto bile acids by gas-liquid chromatography and gas-liquid chromatography-mass spectrometry. One strain was shown to contain a NAD-dependent 3 beta-hydroxysteroid dehydrogenase. Enzyme production was constitutive in the absence of added bile acids. The specific enzyme activity was significantly reduced by growth medium supplementation with 3-keto bile acids, with trisubstituted acids being more effective than disubstituted ones. A pH optimum of 10.0 to 10.2 was found after partial purification by DEAE-cellulose chromatography. A molecular weight of about 56,000 was established. 3 beta-hydroxysteroid dehydrogenase activity was also found in the membrane fraction after solubilization with Triton X-100, suggesting that the enzyme was originally membrane bound. The enzyme reduced a 3-keto group in unconjugated and conjugated bile acids, lower Km values being demonstrated with disubstituted than with trisubstituted bile acids. Keto functions at C-7 and C-12 further reduced the Km value. The enzyme was found to be partially heat labile (86% inactivation at 50 degrees C for 10 min).

3-Hydroxysteroid Dehydrogenases↗
PubMed1975

Multiple forms of 7-alpha-hydroxysteroid dehydrogenase in selected strains of Bacteroides fragilis.

Multiple forms of 7-alpha-hydroxysteroid dehydrogenase were detected in six of nine strains of Bacteroides fragilis. The enzymes differed with respect to pyridine nucleotide specificity, thermal stability, divalent metal cation requirement, and elution profilies from Sephadex G-200 columns. The nicotinamide adenine dinucleotide phosphate (NADP)-dependent enzyme required divalent metal cations, preferentially Mn-2+ (Km, 57 muM), for maximum catalytic activity. The NADP-dependent enzyme was labile at 65 C for 10 min, whereas the nicotinamide adenine dinucleotide (NAD)-dependent enzyme was stable at 65 C for 10 min. The specific activity of both the NAD- and NADP-dependent enzymes in crude extracts increased markedly (15- and 7.5-fold, respectively) during the transition from exponential- to stationary-phase growth in glucose medium containing 0.5 mM sodium cholate. The time course of apparent enzyme induction correlated temporally with the transformation of the 7-alpha-hydroxy group of cholate in the culture supernatant fluid. Both NAD- and NADP-dependent 7-alpha-hydroxysteroid dehydrogenase activities were found to be widely, but not universally, distributed in different strains and subspecies of B. fragilis. No NAD- or NADP-dependent 7-alpha-hydroxysteroid dehydrogenase activity could be detected in B. fragilis subsp. vulgatus Virginia Polytechnic Institute (VPI) no. 4245, subsp. thetaiotaomicron VPI 0061-1, or subsp. distasonis VPI 4243.

Bacteroides↗
PubMed1985

Kinetic comparison of the 3 beta-hydroxysteroid dehydrogenase activity in human placenta, chorion laeve, and ovary.

Recent studies from our laboratory and others have shown that Km values for steroid substrates of the 3 beta-hydroxysteroid dehydrogenase in the human placenta were in the nanomolar range compared with micromolar values previously described. The purpose of the present study was to measure the kinetic parameters of the 3 beta-hydroxysteroid dehydrogenase in other human tissues, namely the ovary and chorion laeve, and to determine whether they were similar to those of the placental enzyme. In chorion laeve microsomes the 3 beta-hydroxysteroid dehydrogenase had Km values for dehydroepiandrosterone and pregnenolone similar to those found in placenta. Microsomes from human ovaries, on the other hand, had Km values for both substrates 10- to 20-fold higher. However, the ability of various steroids to inhibit the ovarian enzyme was similar to that previously described from the placenta and the chorion laeve.

3-Hydroxysteroid Dehydrogenases↗
PubMed1979

Effects of unilateral orchidectomy on rat epididymal delta 4-5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase.

The effects of unilateral orchidectomy on the adult rat epidiymal testosterone metabolizing enzymes, delta 4-5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase, are investigated. Five weeks following unilateral orchidectomy, it is found that the activity of 3 alpha-hydroxysteroid dehydrogenase per organ is not altered, whereas delta 4-5 alpha-reductase activity decreased by more than 80% on the side of the orchidectomy. Neither accessory sex tissue weights, ventral prostate and seminal vesicles, nor the concentration of circulating testosterone, luteinizing hormone, follicle-stimulating hormone, or prolactin is altered by unilateral orchidectomy. These data indicate that (1) epididymal 3 alpha-hydroxysteroid dehydrogenase activity can be maintained by circulating androgens and that (2) the major factor regulating delta 4-5 alpha-reductase activity is not a substance secreted by the testes into the peripheral circulation. It is suggested that a substance directly secreted into the epididymis by the testis regulates epididymal delta 4-5 alpha-reductase activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1976

Histochemical localization of some hydroxysteroid dehydrogenases in the mouse epididymis.

The mouse epididymis was studied to localize histochemically a number of hydroxysteroid dehydrogenases in the various zones. The epithelium of the posterior half of the initial segment (head) and the anterior half of the middle segment (body) shows a strong reaction for delta5-3beta-, 3alpha,5alpha-, 3alpha,5beta-, 11beta, 16alpha-, 17beta, 20alpha-hydroxysteroid dehydrogenases. This activity attenuates posteriorly. Only the 11beta-hydroxysteroid dehydrogenase is present throughout the length of the epididymis. The luminal contents of the middle segment also show the histochemical utilization of a number of steroids.

Animals↗
PubMed2004

Impaired 11-beta hydroxysteroid dehydrogenase type 2 activity in sweat gland ducts in human essential hypertension.

The enzyme 11-beta hydroxysteroid dehydrogenase type 2 plays a major role in blood pressure regulation. It metabolizes glucocorticoid hormones into derivatives with low affinity for the mineralocorticoid receptor, preventing its permanent occupancy by circulating cortisol, which is 100- to 1000-fold more abundant than aldosterone in the plasma. Inactivating mutations of the enzyme result in severe hypertension, as seen in children with apparent mineralocorticoid excess syndrome. In patients with essential hypertension, however, attempts to evidence enzyme deficiency have been inconclusive. In this pilot study, its catalytic activity was measured directly in aldosterone-sensitive sweat gland ducts collected from skin biopsy samples of 10 male normotensive subjects and 10 subjects with essential hypertension (more than 140 to 90 mm Hg) with no sign of hypermineralocorticism. Isolated ducts were assayed for nicotinamide-dinucleotide-dependent dehydrogenase activity (transformation of tritiated corticosterone into tritiated-11 dehydrocorticosterone, as measured by high-pressure liquid chromatography). Hypertensive patients exhibited significantly lower 11-beta hydroxysteroid dehydrogenase type 2 activity (9.7+/-4.7 femtomoles per 3 mm length of duct and per 10 minutes incubation, median+/-SD) than did normotensive subjects (15.9+/-2.6). Such defect was undetectable using the classical urinary corticosteroid metabolism indexes, probably because of compensatory mechanisms. Relations between these findings and blood pressure levels should benefit from direct enzyme measurements in the vasculature. In conclusion, this cross-sectional study points to partial 11-beta hydroxysteroid dehydrogenase type 2 deficiency as a novel feature of essential hypertension, which should stimulate search for new signaling pathways and therapeutical targets.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗
PubMed1984

Maximal testosterone production in Leydig cells from inbred mice relates to the activity of 3 beta-hydroxysteroid dehydrogenase-isomerase.

We previously described significant differences in maximal testosterone production by Leydig cells from the following strains of inbred mice: C57BL/10J, C57BL/6J, DBA/2J, and C3H/HeJ. To evaluate whether these differences in maximal testosterone production related to the activities of the steroidogenic enzymes of the smooth endoplasmic reticulum of Leydig cells from these strains, the activities of 3 beta-hydroxysteroid dehydrogenase-isomerase, 17 alpha-hydroxylase, C17-20 lyase, and 17-ketosteroid reductase were measured in homogenates of purified Leydig cells using 3H-labeled substrates and measuring the amounts of 3H products formed. Maximal and basal testosterone production were determined by incubating aliquots of Leydig cells for 2 h in the presence or absence of 30 pM hCG. Maximal testosterone production by Leydig cells from C57BL/10J and C57BL/6J mice was significantly greater than that by Leydig cells from DBA/2J and C3H/HeJ mice. No difference in basal testosterone production was observed among the strains. Among the four enzymes studied, only 3 beta-hydroxysteroid dehydrogenase-isomerase activity was significantly correlated with hCG-stimulated testosterone production by Leydig cells from the four strains of mice. In addition, when equivalent numbers of Leydig cells from each strain were incubated with an equal concentration of [3H]pregnenolone, a similar difference in [3H] testosterone production was observed among the four strains, as was seen with hCG-stimulation. Leydig cells from C57BL/10 and C57BL/6J mice left less [3H]pregnenolone unmetabolized and produced higher amounts of [3H]testosterone than Leydig cells from DBA/2J and C3H/HeJ mice. There was a significant negative correlation between the amount of pregnenolone unmetabolized and the amount of testosterone produced. These data suggest that 3 beta-hydroxysteroid dehydrogenase-isomerase may be important in determining the differences in hCG-stimulated testosterone production by Leydig cells from the four strains of mice.

3-Hydroxysteroid Dehydrogenases↗
PubMed1999

Characterization of molecular and catalytic properties of intact and truncated human 17beta-hydroxysteroid dehydrogenase type 2 enzymes: intracellular localization of the wild-type enzyme in the endoplasmic reticulum.

Human 17beta-hydroxysteroid dehydrogenase (17HSD) type 2 is a widely distributed enzyme that primarily converts the highly active 17beta-hydroxysteroids to their inactive keto forms. In the present study, full-length human 17HSD type 2 was localized in the endoplasmic reticulum using a double immunofluorescence labeling technique. As a consequence of its strong membrane interaction, full-length human 17HSD type 2 could not be solubilized as a biologically active form in vitro. However, by deleting the first 29 amino acids from the N-terminus, we were able to purify a catalytically active enzyme from the cytosolic fraction of Sf9 insect cells. Biochemical and catalytic properties of the purified truncated human 17HSD type 2 protein confirm its suitability for structure-function analyses of the enzyme. Both intact and truncated 17HSD type 2 enzymes efficiently catalyzed the oxidation of estradiol, testosterone, dihydrotestosterone, androstenediol, and 20alpha-dihydroprogesterone. The oxidation of estradiol brought about by human 17HSD type 2 was effectively inhibited by several other steroidal compounds, such as 2-hydroxyestradiol, 5beta-androstan-3alpha,17beta-diol, 5alpha-androstan-3alpha,17beta-diol, and 5alpha-androstan-3beta,17beta-diol. The broad substrate specificity of human 17HSD type 2 together with its predominant oxidative activity and intracellular location, as observed in this study, indicate the physiological role of the enzyme to be primarily an inactivator of highly active 17beta-hydroxysteroids.

17-Hydroxysteroid Dehydrogenases↗
PubMed1998

Expression cloning of a novel estrogenic mouse 17 beta-hydroxysteroid dehydrogenase/17-ketosteroid reductase (m17HSD7), previously described as a prolactin receptor-associated protein (PRAP) in rat.

17 beta-Hydroxysteroid dehydrogenases/17-ketosteroid reductases (17HSDs) modulate the biological activity of certain estrogens and androgens by catalyzing reductase or dehydrogenase reactions between 17-keto- and 17 beta-hydroxysteroids. In the present study, we demonstrate expression cloning of a novel type of 17HSD, chronologically named 17HSD type 7, from the HC11 cell line derived from mouse mammary gland. The cloned cDNA, 1.7 kb in size, encodes a protein of 334 amino acids with a calculated molecular mass of 37,317 Da. The primary structure contains segments characteristic of enzymes belonging to the short-chain dehydrogenase/reductase superfamily. Strikingly, mouse 17HSD type 7 (m17HSD7) shows 89% identity with a recently cloned rat protein called PRL receptor-associated protein (PRAP). The function of PRAP has not yet been demonstrated. The enzymatic characteristics of m17HSD7 and RT-PCR-cloned rat PRAP (rPRAP) were analyzed in cultured HEK-293 cells, where both of the enzymes efficiently catalyzed conversion of estrone (E1) to estradiol (E2). With other substrates tested no detectable 17HSD or 20 alpha-hydroxysteroid dehydrogenase activities were found. Kinetic parameters for m17HSD7 further indicate that E1 is a preferred substrate for this enzyme. Relative catalytic efficiencies (Vmax/K(m) values) for E1 and E2 are 244 and 48, respectively. As it is the case with rPRAP, m17HSD7 is most abundantly expressed in the ovaries of pregnant animals. Further studies show that the rat enzyme is primarily expressed in the middle and second half of pregnancy, in parallel with E2 secretion from the corpus luteum. The mRNA for m17HSD7 is also apparent in the placenta, and a slight signal for m17HSD7 is found in the ovaries of adult nonpregnant mice, in the mammary gland, liver, kidney, and testis. Altogether, because of their similar primary structures, enzymatic characteristics, and the tissue distribution of m17HSD7 and rPRAP, we suggest that rPRAP is rat 17HSD type 7. Furthermore, the results indicate that 17HSD7 is an enzyme of E2 biosynthesis, which is predominantly expressed in the corpus luteum of the pregnant animal.

17-Hydroxysteroid Dehydrogenases↗
PubMed1983

Histochemical location of 17 beta-hydroxysteroid oxidoreductase in the adult and infantile human testis.

17 beta-Hydroxysteroid oxidoreductase in the human testis was investigated histochemically using tissues obtained from seven patients with undescended testis or varicocele at the time of orchiopexy or high ligation of spermatic vein. Formazan precipitates were formed from nitro-blue tetrazolium in the tissue utilizing hydrogen released by oxidation of testosterone, which is catalyzed by the reductase function of 17 beta-hydroxysteroid oxidoreductase. The precipitates were formed specifically in the presence of 17 beta-hydroxy-C19-steroids under the conditions employed in the present study. In infantile testes, the precipitates were formed in cytoplasm of immature Sertoli cells, while in pubertal or adult testes, marked formazan precipitates were found in cytoplasm of both Sertoli and Leydig cells. The results indicate the presence of two distinct 17 beta-hydroxysteroid oxidoreductases in the human testis; one in Sertoli cells and detectable independent of age and the other only in functional Leydig cells.

17-Hydroxysteroid Dehydrogenases↗
PubMedDate not supplied

Purification and properties of the soluble 17 beta-hydroxysteroid dehydrogenase of rabbit uterus.

17 beta-Hydroxysteroid dehydrogenase activity towards estradiol-17 beta has been demonstrated in the 105,000 x g supernatant of rabbit uterus. Hydroxylapatite chromatography of the enzyme activity isolated by ammonium sulfate precipitation, gel filtration and DEAE-cellulose chromatography yielded a single 17 beta-hydroxysteroid dehydrogenase activity. Further purification of the enzyme preparation by isoelectric focusing resulted in multiple peaks of activity. The molecular weight of the enzyme, caculated from mobility data on Sephadex gel, is approximately 64,000. Some properties of partially purified 17 beta-hydroxysteroid dehydrogenase activity have been studied. Estradiol-17 beta reacts at a faster rate than testosterone. The Km for estradiol is 4.16 x 10(-5) mol/l for the NAD-linked enzyme activity and 4.37 x 10(-5) mol/l when NADP as cofactor was used. The ratio of the maximal velocity for NADP to that for NAD was 1.42. The pH-optimum for estradiol appears between 9.5 and 10.5 and for estrone between 5.5 and 6.5. The enzyme appears to be of the sulfhydryl type.

17-Hydroxysteroid Dehydrogenases↗
PubMedDate not supplied

3 beta-hydroxysteroid oxidoreductase in suspension cultures of Digitalis lanata EHRH.

A 3 beta-hydroxysteroid oxidoreductase was isolated and characterized in the microsomes of Digitalis lanata cell cultures. The enzyme catalyzes the conversion of 5 alpha-pregnane-3,20-dione to 5 alpha-pregnan-3 beta-ol-20-one and requires NAD(P)H2. The enzyme was found to have a pH optimum of 8.0. The reaction had an optimum incubation temperature of 25 degrees C with linear reduction for the first 4 h, reaching maximum enzyme activity after 7 h. Substrate kinetics for 5 alpha-pregnane-3,20-dione and NADPH2 resulted in apparent Km-values of 18.5-20 microM for 5 alpha-pregnane-3,20-dione and 50-120 microM for the co-substrate NADPH2. In order to localize 3 beta-hydroxysteroid oxidoreductase differential centrifugation as well as linear sucrose density gradient centrifugation were performed. The results obtained lead to the conclusion that 3 beta-hydroxysteroid oxidoreductase is not associated with a single cell compartment, but consists of a major soluble part and a markedly smaller part of endoplasmic reticulum-associated activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1978

The hormonal regulation of hepatic microsomal 11beta-hydroxysteroid dehydrogenase activity in the rat.

Hepatic microsomal 11beta-hydroxysteroid dehydrogenase activity is higher in male than in female rat liver. Gonadectomy on day 25 of life only affects the activity in the adult male animal, causing a decrease towards the normal female level. Administration of testosterone to gonadectomized rats of either sex causes the induction of typical male activity levels. On the basis of these experiments, this enzyme activity may be classified as an drogen-dependent. However, 11beta-hydroxysteroid dehydrogenase differs from other known androgen-dependent activities in that administration of oestradiol to gonadectomized animals of either sex causes a further significant repression of the activity to levels close to the limits of detection. Hypophysectomy on day 50 of life does not affect the activity in 75 day-old male rats, but causes the appearance of typically male activity levels in females. These results indicate that the hypophysis exerts a repressive influence on hepatic 11beta-hydroxysteroid dehydrogenase in female rats. The facts that this activity is not influenced by androgen or oestrogen administration once the pituitary has been removed demonstrates the obligatory role of the hypophysis for sex hormone action.

Animals↗
PubMed1994

3 beta-Hydroxysteroid dehydrogenase activity and gestagen concentrations in bovine cotyledons and caruncles during gestation and parturition.

3 beta-Hydroxysteroid dehydrogenase (3 beta-HSD) activity in bovine cotyledons was much higher than in caruncles throughout the gestation period. The activity of this enzyme in cotyledons increased greatly to 150.6 +/- 5.8 pmol min-1 mg-1 protein during the seventh month of gestation, reached a peak of 221.0 +/- 34.9 pmol min-1 mg-1 protein during the eighth month, and decreased at parturition. Progesterone and 20 alpha-hydroxyprogesterone concentrations in cotyledons also increased sharply to 2.69 +/- 0.30 and 2.15 +/- 0.42 ng mg-1 protein, respectively, during the seventh month of gestation, reaching peaks of 2.86 +/- 0.47 and 2.51 +/- 0.36 ng mg-1 protein, respectively, during the eighth month and decreasing at parturition, in a manner similar to the activity of 3 beta-hydroxysteroid dehydrogenase. The fluctuation of 17 alpha-hydroxyprogesterone concentration in cotyledons was different from that of progesterone and 20 alpha-hydroxyprogesterone. These findings indicate that the activity of 3 beta-hydroxysteroid dehydrogenase in the placenta is enhanced during the third trimester, and progesterone synthesized in the cotyledons is converted concurrently to 20 alpha-hydroxyprogesterone before progesterone is transferred to the fetal blood.

17-alpha-Hydroxyprogesterone↗