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PubMed1995

Comparison of 11 beta-hydroxysteroid dehydrogenase in spontaneously hypertensive and Wistar-Kyoto rats.

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) modulates glucocorticoid interactions with mineralocorticoid and glucocorticoid receptors in vivo, by converting 11 beta-hydroxyglucocorticoids to their inactive 11-ketone derivatives. Defective 11 beta-oxidation of glucocorticoids has been associated with hypertension. The objective of this study was to investigate whether 11 beta-HSD contributes to the occurrence of hypertension in spontaneously hypertensive rats (SHRs). The liver and kidney microsomal oxidations of corticosterone (the physiological glucocorticoid in rats) in organs from juvenile (3 weeks old) and adult (3 months old) SHR and Wistar-Kyoto (WKY) rats, with NAD and NADP, show no differences between rat strains. For cortisol, with NADP, adult SHRs show (1.3-3 times; P < 0.05) lower kidney microsomal oxidation rates. The liver microsomal reduction of cortisone shows remarkable interstrain differences; with NADH, reduction is conducted only by adult WKY rats, whereas with NADPH, juvenile animals show similar reduction rates, but at adulthood, only WKYs reduce cortisone. Using Western blot analysis with antibodies against 11 beta-HSD1, positive signals are obtained only for liver microsomes, appearing somewhat lower in SHRs for juvenile but not adult animals. Urinary corticosterone/11-dehydrocorticosterone ratios (measured in adult animals) are not different between rat strains, but are elevated after administration of corticosterone in both strains (although significant only in SHRs). The data provide no indications for exaggerated stimulation of renal corticosteroid receptors, due to modified 11 beta-HSD, in SHRs. However, the experiments suggest the existence of multiple 11 beta-HSDs, in addition to 11 beta-HSD1 and 11 beta-HSD2, some of which may be modified in SHR, but the nature and physiological role of these 11 beta-HSDs is unclear.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1996

11 beta-hydroxysteroid dehydrogenases of the choriocarcinoma cell line JEG-3 and their inhibition by glycyrrhetinic acid and other natural substances.

Mineralocorticoid receptor (MR) selectivity for aldosterone is thought to be exerted by enzymes which inactivate competing glucocorticoids before they bind the receptor. Two different 11 beta-hydroxysteroid dehydrogenases (11 beta-HSD) have been described. 11 beta-HSD-1 is NADP(+)-dependent and has a Km in the micromolar range and bidirectional activity. 11 beta-HSD-2 is NAD(+)-dependent, has a Km in the nanomolar range, exhibits only oxidase activity, and colocalizes with the MR in the kidney, so is likely to serve as the gatekeeper for the MR. We have further characterized 11 beta-HSD activity in JEG-3 cells, a cell line derived from a human choriocarcinoma which was reported to have only the high affinity, NAD(+)-dependent 11 beta-HSD-2. We found that the Km for the conversion of corticosterone to 11-dehydrocorticosterone in intact cells and homogenates was about 16 nM. NAD(+)-dependent corticosterone conversion was equal in the nuclear and mitochondrial fractions and less, but significant, in the microsomal fraction. A high affinity, Km = 40 nM, NADP(+)-dependent enzyme was also found in homogenates. The subcellular distribution of this high affinity activity was greatest in the mitochondria, less in the nuclei, and even less, but still significant, in microsomes. Because of its cofactor dependency, high affinity, and different subcellular distribution, we suggest that this enzyme is neither the 11 beta-HSD-1 nor the 11 beta-HSD-2 and have named it 11 beta-HSD-3. Conversion of 11-dehydrocorticosterone to corticosterone did not occur in intact cells or in homogenates incubated with NADH or NADPH. Enzyme activity in intact cells was inhibited by glycyrrhetinic acid, carbenoxolone, progesterone, 5 beta-dihydroprogesterone, and 5 alpha-dihydroprogesterone, but not bile acids.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1996

The 11 beta-hydroxysteroid dehydrogenase type II enzyme: biochemical consequences of the congenital R337C mutation.

The 11 beta-hydroxysteroid dehydrogenase type II enzyme (11 beta HSD2) converts cortisol to cortisone, allowing the non-selective mineralocorticoid receptor to bind aldosterone. When the activity of this enzyme is compromised, as occurs in licorice intoxication or in the congenital syndrome of apparent mineralocorticoid excess (AME), there is marked sodium retention, hypokalemia, and hypertension. The first proof that this enzyme was defective in AME came from the identification of the R337C mutation in a number of siblings with the syndrome. Subsequent expression studies showed that the mutant had a Km one order of magnitude higher than the wild-type enzyme while in the cell-free system it was without detectable activity. In the present work we have extended our studies on this mutant and provide evidence that the mutant protein may also partially inhibit the wild-type enzyme in heterozygotes. Furthermore, experiments incorporating the protein synthesis inhibitor cycloheximide show that the mutant enzyme is less stable than the wild-type activity in intact cells. These results suggest that mutations in the 11 beta HSD2 enzyme may have multiple consequences for the mineralocorticoid target cell.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1996

11 beta-Hydroxysteroid dehydrogenases: key enzymes in determining tissue-specific glucocorticoid effects.

Recent studies have demonstrated that the interconversion of active and inactive glucocorticoids plays a key role in determining the specificity of the mineralocorticoid receptor and controlling local tissue glucocorticoid receptor activation. Two distinct isoforms of the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) have been identified. 11 beta-HSD1 is NADPH-dependent and at its major site of action (the liver) is a reductase, converting cortisone to cortisol (11-dehydrocorticosterone to corticosterone in the rat). 11 beta-HSD2 is NAD-dependent, is present in tissues such as the kidney and placenta, and converts cortisol to cortisone (corticosterone to 11-dehydrocorticosterone in the rat). Congenital or acquired deficiency of 11 beta-HSD2 produces the syndrome of apparent mineralocorticoid excess (SAME) in which cortisol gains access to the unprotected nonspecific mineralocorticoid receptor. The congenital deficiency is associated with mutations in the gene encoding the kidney isoform of 11 beta-HSD2; the acquired form results from inhibition of the enzyme by licorice, carbenoxolone, ACTH-dependent steroids in the ectopic ACTH syndrome, and possibly circulating inhibitors of the enzyme. This paper focuses on recent evidence, which suggest that low levels of placental 11 beta-HSD2 result in increased exposure of the fetus to maternal glucocorticoid and low birth weight. In animal studies using the rat we have shown that birth weight is correlated positively and placental weight negatively with the level of placental 11 beta-HSD. Thus animals with low birth weight and large placentae were those likely to be exposed to the highest level of maternal glucocorticoid. In man a similar relationship was found with birth weight being significantly correlated either with placental 11 beta-HSD activity or with the extent of cortisol inactivation by isolated perfused placental cotyledons. Administration of dexamethasone (which is poorly metabolized by placental 11 beta-HSD2) to pregnant rats resulted in decreased birth weight and the development of hypertension in the pups when adult. The same results were obtained when pregnant rats were given carbenoxolone, an inhibitor of placental 11 beta-HSD2. Low protein diet during pregnancy in the rat resulted in low birth weight of the pups, increased placental weight but decreased placental 11 beta-HSD activity, and adult hypertension. Thus increased glucocorticoid exposure of the fetus secondary to a failure of the normal inactivation of maternal glucocorticoid by the placental may be an important mechanism linking changes in the in utero environment and common adult diseases.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1996

Differential effect of adrenocorticosteroids on 11 beta-hydroxysteroid dehydrogenase bioactivity at the anterior pituitary and hypothalamus in rats.

11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD) is a microsomal enzyme that catalyzes the dehydrogenation of cortisol (F) to cortisone (E) in man and corticosterone (B) to 11-dehydrocorticosterone (A) in rats. 11 beta-OHSD has been identified in a wide variety of tissues. The differential distribution of 11 beta-OHSD suggests that this enzyme has locally defined functions that vary from region to region. The aim of this study was to investigate the effects of the glucocorticoids B and dexamethasone (DM), the mineralocorticoid deoxycorticosterone (DOC), and the inhibitors of 11 beta-OHSD glycyrrhizic acid (Gl) and glycyrrhetinic acid (GE) on 11 beta-OHSD bioactivity at the hypothalamus (HT) and anterior pituitary (AP). Male Wistar rats were treated with GI or were adrenalectomized (ADX) and treated with either B, DM, or DOC for 7 days. All treatments were in vivo except GE, which was used in vitro. At the end of treatment, homogenates of HT and AP were assayed for 11 beta-OHSD bioactivity, expressed as the percentage conversion of B to A in the presence of NADP, 11 beta-OHSD bioactivity is significantly higher (P < 0.0001) in the AP compared with the HT. Adrenalectomy significantly increased the enzyme activity in the AP (P < 0.05), an effect reversed by B or DM. ADX rats treated with DOC showed decreased enzyme activity in the AP (P < 0.001) but increased the activity in the HT (P < 0.0001). Gl increased activity in both HT and AP, whereas GE decreased activity significantly. We conclude that the modulation of 11 beta-OHSD is both steroid specific and tissue specific.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1993

Ovarian 11 beta-hydroxysteroid dehydrogenase: potential predictor of conception by in-vitro fertilisation and embryo transfer.

Cortisol is converted to the inactive glucocorticoid, cortisone, in several tissues by 11 beta-hydroxysteroid dehydrogenase (11 beta HSD). We have recently measured 11 beta HSD activity in cultured human granulosa-lutein cells recovered from patients undergoing in-vitro fertilisation and embryo transfer (IVF-ET). We now report an association between the outcome of IVF-ET and 11 beta HSD activity in these cells. Of the 64 patients studied, 32 had detectable 11 beta HSD activity and none became pregnant; whereas 76% of the remaining "11 beta HSD-negative" patients achieved pregnancies. Hence 11 beta HSD activity may predict the outcome of IVF-ET.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1997

Cellular localization and developmental regulation of 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta-HSD1) gene expression in the ovine placenta.

This study was designed to examine the cellular localization and developmental regulation of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) type 1 gene expression in the ovine placenta. Placental tissues were collected at discrete times between days 59 and 143 of pregnancy (term = 145 days). Levels of 11 beta-HSD1 mRNA were determined by Norther blot analysis. The level of both dehydrogenase and reductase activities of 11 beta-HSD1 was assessed by a radiometric conversion assay using cortisol and cortisone as physiological substrates. The cellular localization of 11 beta-HSD1 protein was determined by standard immunohistochemical technique using a polyclonal antibody specific for the ovine protein. High levels of 11 beta-HSD1 mRNA were detected in the placenta by day 59, and there was a trend towards a decrease between days 98-103 and 125-128 (P = 0.06). The level of placental 11 beta-HSD1 mRNA remained unchanged thereafter. Levels of both 11 beta-HSD1 dehydrogenase and reductase activities followed a similar pattern except that in both cases there was a significant decrease between 98-103 and 125-128 (P < 0.05). Moreover, under the present assay conditions, the dehydrogenase activity was always predominant, suggesting that the net effect of placental 11 beta-HSD1 activity would lead to glucocorticoid inactivation. Thus, the decreased 11 beta-HSD1 activity in the placenta at days 125-128 was consistent with, and may help to explain, the apparent increase in the placental transfer of cortisol from mother to fetus during that time. Throughout pregnancy, intense 11 beta-HSD1 immunoreactivity was detected in fetal trophoblastic cells, maternal stromal cells and blood vessels. In contrast, maternal syncytium was immunonegative before day 125, but became immunopositive thereafter. The observed predominant direction of 11 beta-HSD1 activity in vitro and its pattern of localization in the ovine placenta are consistent with the hypothesis that placental 11 beta-HSD protects the fetus from adverse effects of maternal glucocorticoids by inactivating glucocorticoids locally.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1986

Camphoroquinone reduction: another reaction catalyzed by rat liver cytosol 3 alpha-hydroxysteroid dehydrogenase.

A new purification scheme is described for the female rat liver cytosolic enzyme dually catalyzing the oxidation of androsterone (3 alpha-hydroxysteroid:NAD(P)+ oxidoreductase, EC 1.1.1.50) and acenaphthenol (trans-1,2-dihydrobenzene-1,2-diol:NADP+ oxidoreductase, EC 1.3.1.20). This purification procedure yielded the most highly purified preparation of this enzyme thus far published as adjudged from its androsterone oxidation activity. In addition, we have demonstrated that this purified enzyme also catalyzes the reduction of camphoroquinone, a natural monoterpene, non-aromatic quinone. The nature of the products of the camphoroquinone reduction has been partially elucidated and agrees with previously published results (Robertson, J.S. and Solomon, E. (1971) Biochem. J. 121, 503-509). Kinetic studies of the metabolism of androsterone, camphoroquinone and acenaphthenol by the enzyme have been performed, yielding respective Km and Vmax values. The results of these studies allow a clarification of the mechanism of action of this enzyme, particularly with respect to its dihydrodiol dehydrogenase activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Glycyrrhetinic acid bound to 11 beta-hydroxysteroid dehydrogenase in rat liver microsomes.

A binding protein which exhibits high affinity to [3H]glycyrrhetinic-acid in the rat liver microsomal fraction was solubilized with 0.2% Triton DF-18 and then purified to homogeneity. The equilibrium dissociation constant of the [3H]glycyrrhetinic-acid binding reaction and the maximal concentration for the binding of the purified protein, as determined by Scatchard plot analysis, were 27.6 nM and 7.79 nmol/mg protein, respectively. The molecular mass of the subunit (34 kDa) and 30 amino acids of N-terminal sequence of the purified protein were entirely the same as those of the reported 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD). In each purification step, the recovery and purification (fold) of the glycyrrhetinic-acid binding activity corresponded to the values of 11 beta-HSD activity. These results show that the purified [3H]glycyrrhetinic-acid binding protein is 11 beta-HSD. From the molecular mass of 11 beta-HSD (135 kDa) and the maximal concentration of the binding site, it was calculated that one glycyrrhetinic acid molecule binds to one 11 beta-HSD molecule. The inhibitory effects of various glycyrrhetinic-acid derivatives on [3H]glycyrrhetinic acid binding and 11 beta-HSD activity indicate that the C30-carboxyl and C11-carbonyl groups of glycyrrhetinic acid are the principal structures for the 11 beta-HSD inhibition.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1995

Mutations in putative glycosylation sites of rat 11 beta-hydroxysteroid dehydrogenase affect enzymatic activity.

11 beta-hydroxysteroid dehydrogenase (11-HSD) catalyzes the interconversion of corticosterone and 11-dehydrocorticosterone in rats, or cortisol and cortisone in humans. The 'liver' or 'Type I' isozyme is a widely distributed glycoprotein that utilizes NADP+ as a co-factor. To study the role of glycosylation in maintaining enzymatic activity, we introduced mutations into the two potential N-linked glycosylation sites (asparagine-X-serine, residues 158-160 and 203-205) predicted from the rat cDNA sequence. Mutagenesis was performed by a PCR based technique, and wild-type (WT) and mutant cDNAs were expressed in Chinese hamster ovary cells after cloning into the pCMV4 vector. At each putative glycosylation site, asparagine (N) was changed to glutamine (Q) or aspartic acid (D), and serine (S) changed to alanine (A). All three modifications of the first site (N158Q, N158D, S160A) had minimal (75-100% of WT) effects on dehydrogenase activity and caused a mild (50-75% of WT) decrease in reductase activity. In contrast, mutations at the second site had marked effects, with N203Q and N203D completely abolishing both dehydrogenase and reductase activities and S205A decreasing both activities to about 20% of WT. The double mutation of S160A and S205A also abolished all activity, even though the enzyme carrying each mutation alone was, at least, partially active. The results suggest that N203 (which is highly but not completely conserved in short chain dehydrogenase enzymes) is essential for activity of 11-HSD. N-linked glycosylation may be necessary for full activity or stability of the enzyme.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1989

Renal epithelial cell lines (BSC-1, MDCK, LLC-PK1) express 11 beta-hydroxysteroid dehydrogenase activity.

Renal tissue of several species has been shown to express considerable 11 beta-hydroxysteroid dehydrogenase (11-HSD, EC 1.1.1.146) activity. However, it is uncertain as to which renal cell types exhibit 11-HSD activity. In the present study, we investigated corticosterone metabolism in BSC-1 cells, a continuous renal epithelial cell line derived from the African green monkey (Cercopithecus aethiops). In incubation experiments using 3H-labelled corticosterone and HPLC, we have demonstrated oxidative 11-HSD activity in intact monolayers of BSC-1 cells as well as in BSC-1 cell homogenates. 11-HSD activity in cell homogenates could be stimulated 7-9-fold by the addition of exogenous NADP+ (1 mM). In contrast, no reductive 11-HSD could be detected either in intact cells or in cell homogenates under various experimental conditions which were designed to favor reductive 11-HSD activity. Pilot experiments were performed in cell homogenates from two other renal epithelial cell lines derived from canine (MDCK) and porcine (LLC-PK1) kidney. They also revealed oxidative but no reductive 11-HSD activity. The data provide evidence for an epithelial localization of renal oxidative 11-HSD activity.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1984

In vitro effects of PGF2 alpha and a metabolically stable derivative on 20 alpha-hydroxysteroid-dehydrogenase activity in corpora lutea isolated from pseudopregnant rat ovaries.

Single intact corpora lutea were isolated from pseudopregnant rat ovaries stimulated with PMSG and HCG. The activity of 20 alpha-hydroxysteroid-dehydrogenase (20 alpha-OH-SDH) was measured at various stages of pseudopregnancy. The influence of PGF2 alpha or a metabolically stable PGF2 alpha-derivative on this enzyme in vitro was assessed. 20 alpha-OH-SDH activity was low from day 6 to 8, started to rise on day 10 and reached a maximum on day 14 after administration of HCG. The enzyme could be stimulated by the PGF2 alpha-derivative on day 10 and 11 but not on day 6, 8, when basal enzyme activity was still very low or on 12 and 14 of pseudopregnancy when the enzyme had already reached maximal levels. PGF2 alpha or its derivative had no effect on enzyme activity in a cytosolic fraction indicating that particulate cell constituents were required for this process. PGE2 as well as cycloheximide (an inhibitor of protein biosynthesis) were without influence on enzyme stimulation. dB-cAMP but not dB-cGMP decreased enzyme activity. Ca2+ -ions were required for the stimulation of 20 alpha-OH-SDH activity. It is concluded that PGF2 alpha or its stable derivative may modulate ovarian steroid metabolism by acute stimulation of luteal 20 alpha-OH-SDH.

20-Hydroxysteroid Dehydrogenases↗
PubMed1984

Binding of prostaglandin F2 alpha and 20 alpha-hydroxysteroid-dehydrogenase activity of immature rat ovaries throughout pseudopregnancy.

PGF2 alpha is involved in the initiation of progesterone decline in the late luteal phase in the pseudopregnant rat. 20 alpha-Hydroxysteroid- dehydrogenase (20 alpha-OH-SDH), an important enzyme in progesterone metabolism, may participate in luteal regression. It was therefore of interest to investigate whether prostaglandin F2 alpha (PGF2 alpha) receptor binding in membrane particles and 20 alpha-OH-SDH activity in a cytosolic fraction in superovulated ovaries of immature rats are related. Scatchard analysis of the radioligand binding data revealed two classes of PGF2 alpha receptors (KD 10(-10) mol/l and 10(-8) mol/l). The number of binding sites varied from day 1 through day 21 of pseudopregnancy. Maximal binding/mg protein was obtained on day 7 with a gradual decrease until day 21 after HCG administration. 20 alpha-OH-SDH activity was low in 1 to 9 days old corpora lutea and increased markedly during days 11 to 13. Maximal enzyme activity was monitored on days 15 to 21 after administration of HCG. The time dependent increase in 20 alpha-OH-SDH activity was partially suppressed by the treatment of the rats with indomethacin, a potent inhibitor of prostaglandin biosynthesis. Since PGF2 alpha-receptor content does not coincide with the increase in enzyme activity (maximal receptor content preceded maximal enzyme activity by about 6 days), PGF2 alpha may not be the only direct factor responsible for the induction of ovarian 20 alpha-OH-SDH, to terminate luteal function.

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↗
PubMed1994

Formation and degradation of dihydrotestosterone by recombinant members of the rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase family.

The structures of cDNA clones encoding four members of the rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) family were characterized. The rat type I, type II and the novel type IV are genuine NAD+/H-dependent 3 beta-HSD isoenzymes. On the other hand, the liver-specific type III protein is a specific 3-keto-reductase (3-KSR) that catalyzes the conversion of 5 alpha-androstane-3-one-17 beta-ol (DHT) and 5 alpha-androstane 3,17-dione (A-dione) into their 3 beta-hydroxy metabolites. The aim of the present study was to further characterize the enzymatic properties of rat types I, III and IV, especially their role in the formation and degradation of DHT after transient expression in intact human HeLa cervical carcinoma, JEG-3 choriocarcinoma or SW-13 adrenal cortex adenocarcinoma cells in culture. The expressed type III 3-KSR in intact HeLa cells catalyzed the reduction of DHT into 3 beta-diol, whereas expression of type I 3 beta-HSD in these cell lines had no significant effect on the basal conversion of DHT into 3 beta-diol, but it did increase the formation of DHT from 3 beta-diol. A-dione is the predominant product obtained when DHT and 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol) are used as substrates in intact JEG-3 and SW-13 cells transfected with rat type I 3 beta-HSD. Furthermore, this predominant 17 beta-HSD activity was also observed in SW-13 cells transfected with the novel rat type IV 3 beta-HSD. The predominance of this 'secondary' 17 beta-HSD activity is also reflected in HeLa cells transfected with type I 3 beta-HSD by the deduced predominant pathway 3 beta-diol-->DHT-->5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol)-->androsterone (ADT), in which formation of 3 alpha-HSD activity of HeLa cells, whereas the other reactions are catalyzed by the type I 3 beta-HSD isoenzyme. This observation thus demonstrates that rat type I 3 beta-HSD may also catalyze the conversion of 3 alpha-diol into ADT through its intrinsic 17 beta-HSD activity. The predominant metabolic pathways observed in the present study could be attributed to preponderant bioavailability of NAD+ and NADPH in the intact transfected cells used.

17-Hydroxysteroid Dehydrogenases↗
PubMed1994

Cloning and tissue distribution of the human 11 beta-hydroxysteroid dehydrogenase type 2 enzyme.

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) is thought to protect the non-selective mineralocorticoid receptor from occupation by glucocorticoids, and to modulate access of glucocorticoids to glucocorticoid receptors resulting in protection of the fetus and gonads. A ubiquitous low affinity NADP+ dependent enzyme (11 beta HSD1) and a tissue specific, high affinity NAD+ dependent form (11 beta HSD2) of 11 beta HSD exist. We now report the isolation of a cDNA coding for human 11 beta HSD2. The new isoform is NAD+ dependent, exclusively dehydrogenase in directionality, inhibited by glycyrrhetinic acid and metabolizes the synthetic glucocorticoid dexamethasone; it displays Km values for corticosterone and cortisol of 5.1 nM and 47 nM, respectively. Sequence alignment shows that 11 beta HSD2 shares 35% identity with 17 beta HSD2, but is only 14% identical with 11 beta HSD1. The 11 beta HSD2 gene is highly expressed in kidney, colon, pancreas and placenta and the message is also present in the ovary, prostate and testis. These data suggest that 11 beta HSD2 plays an important role in modulating mineralocorticoid and glucocorticoid receptor occupancy by glucocorticoids.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1994

A working hypothesis for the regulation of steroidogenesis and germ cell development in the gonads by glucocorticoids and 11 beta-hydroxysteroid dehydrogenase (11 beta HSD).

The relationship between glucocorticoid secretion from the adrenal gland and gonadal function has previously been attributed to central inhibition by the adrenal steroids of pituitary gonadotropin output. This review focuses on the direct actions of glucocorticoids within the gonads, including positive effects on germ cell maturation and both positive and negative effects on the stimulation of gonadal steroidogenesis by LH and FSH. In addition, we address the role in the gonads of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD), which interconverts the glucocorticoids with their inactive 11-ketosteroid derivatives. To date, two isoforms of 11 beta HSD have been described. 11 beta HSD1, purified and cloned from the liver, has a relatively low affinity for glucocorticoids and acts instead as an 11-oxoreductase, whereas the high affinity 11 beta HSD2, first identified in the kidney, acts as an efficient 11 beta-dehydrogenase to inactivate physiological concentrations of glucocorticoid. We propose that in the gonads, 11 beta HSD1 promotes the positive effects of glucocorticoids on germ cell maturation (by increasing the local concentration of active glucocorticoids), whereas a high affinity 11 beta-dehydrogenase activity, consistent with that of 11 beta HSD2, inactivates glucocorticoids and so protects luteal cells from the inhibitory effects of these steroids during the luteal phase of the ovarian cycle.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1995

Detection of human 11 beta-hydroxysteroid dehydrogenase isoforms using reverse-transcriptase-polymerase chain reaction and localization of the type 2 isoform to renal collecting ducts.

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD), responsible for the interconversion of hormonally active cortisol to inactive cortisone, dictates specificity for the mineralocorticoid receptor (MR) in the distal nephron and colon. Two isoforms of human 11 beta-HSD have been cloned, an NADP(H)-dependent (type 1) dehydrogenase/oxo-reductase enzyme, and a high-affinity NAD-dependent (type 2) unidirectional dehydrogenase. Using the reverse-transcriptase polymerase chain reaction (RT-PCR) amplification of RNA extracted from human adult tissues, type 1 11 beta-HSD mRNA was found in decidua, placenta, liver, lung, spleen, kidney medulla, cerebellum and pituitary, but was absent in kidney cortex, sigmoid and rectal colon, salivary gland and thyroid. In contrast, type 2 11 beta-HSD mRNA was found only in placenta and in the classical mineralocorticoid target tissues, kidney cortex, kidney medulla, sigmoid and rectal colon, salivary gland, and colonic epithelial cell lines (AAC1 and RGC28). In situ hybridization studies of renal cortex, cortico-medullary junction and medulla using a 35S-labeled antisense cRNA probe for type 2 human 11 beta-HSD, revealed specific localization of type 2 11 beta-HSD mRNA expression exclusively to renal cortical and medullary collecting ducts. Type 1 and type 2 isoforms of human 11 beta-HSD are expressed in a distinct tissue-specific fashion, in keeping with the proposed differences in their physiological roles. Type 2 11 beta-HSD is found predominantly in mineralocorticoid target tissues where it serves to protect the MR in an autocrine fashion.

11-beta-Hydroxysteroid Dehydrogenases↗