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PubMed1997

Vasopressin potentiates mineralocorticoid selectivity by stimulating 11 beta hydroxysteroid deshydrogenase in rat collecting duct.

Arginine vasopressin (AVP) and corticosteroid hormones are involved in sodium reabsorption regulation in the renal collecting duct. Synergy between AVP and aldosterone has been well documented, although its mechanism remains unclear. Both aldosterone and glucocorticoid hormones bind to the mineralocorticoid receptor (MR), and mineralocorticoid selectivity depends on the MR-protecting enzyme 11 beta hydroxysteroid deshydrogenase (11-HSD), which metabolizes glucocorticoids into derivatives with low affinity for MR. We have investigated whether the activity of 11-HSD could be influenced by AVP and corticosteroid hormones. This study shows that in isolated rat renal collecting ducts, AVP increases 11-HSD catalytic activity. This effect is maximal at 10(-8) M AVP (a concentration clearly above the normal physiological range of AVP concentrations) and involves the V2 receptor pathway, while activation of protein kinase C or changes in intracellular calcium are ineffective. The stimulatory effect of AVP on 11-HSD is largely reduced after adrenalectomy, and is selectively restored by infusion of aldosterone, not glucocorticoids. We conclude that this synergy between AVP and aldosterone in controlling the activity of 11-HSD is likely to play a pivotal role in resetting mineralocorticoid selectivity, and hence sodium reabsorption capacities of the renal collecting duct.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Hypertension in mice lacking 11beta-hydroxysteroid dehydrogenase type 2.

Deficiency of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) in humans leads to the syndrome of apparent mineralocorticoid excess (SAME), in which cortisol illicitly occupies mineralocorticoid receptors, causing sodium retention, hypokalemia, and hypertension. However, the disorder is usually incompletely corrected by suppression of cortisol, suggesting additional and irreversible changes, perhaps in the kidney. To examine this further, we produced mice with targeted disruption of the 11beta-HSD2 gene. Homozygous mutant mice (11beta-HSD2(-/-)) appear normal at birth, but approximately 50% show motor weakness and die within 48 hours. Both male and female survivors are fertile but exhibit hypokalemia, hypotonic polyuria, and apparent mineralocorticoid activity of corticosterone. Young adult 11beta-HSD2(-/-) mice are markedly hypertensive, with a mean arterial blood pressure of 146 +/- 2 mmHg, compared with 121 +/- 2 mmHg in wild-type controls and 114 +/- 4 mmHg in heterozygotes. The epithelium of the distal tubule of the nephron shows striking hypertrophy and hyperplasia. These histological changes do not readily reverse with mineralocorticoid receptor antagonism in adulthood. Thus, 11beta-HSD2(-/-) mice demonstrate the major features of SAME, providing a unique rodent model to study the molecular mechanisms of kidney resetting leading to hypertension.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1997

A non-isotopic method for estimating 11 beta hydroxysteroid dehydrogenase activity in vivo.

11 beta-hydroxysteroid dehydrogenase (11 beta HSD) has both dehydrogenase (11 beta DH) and reductase (11 beta R) activities, which catalyse the interconversion of cortisol and cortisone, and prednisolone and prednisone. This enzyme confers specificity on the mineralocorticoid receptor by local oxidation of cortisol to cortisone. Using radiolabelled cortisol 11 beta HSD activity has been shown to be lower in some cases of essential hypertension. This study investigated a novel approach to estimating 11 beta HSD activity in vivo. Plasma steroid kinetics were investigated following oral hydrocortisone (a substrate for 11 beta DH) and prednisone (a substrate for 11 beta R) in five normotensive volunteers after dexamethasone suppression of endogenous steroid production. This approach was evaluated by inducing partial deficiency of 11 beta HSD in the volunteers who took liquorice (to inhibit 11 beta DH) and then carbenoxolone (to inhibit both 11 beta DH and 11 beta R). The ratio of cortisol to prednisolone (formed from prednisone) provided a measure of the activity of both 11 beta DH and 11 beta R. At 75 min after the steroid bolus the ratio increased from 1.1 (0.6-1.3) (median, range) under control conditions to 1.2 (0.8-1.7) after liquorice (P = 0.01, n = 5), and 2.0 (1.3-5.9) after carbenoxolone (P = 0.02, n = 5). It may therefore be applied to the measurement of 11 beta HSD activity in vivo in large numbers of hypertensive patients without the use of radioisotopes.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2003

11 Beta-hydroxysteroid dehydrogenases in the brain: two enzymes two roles.

Glucocorticoids affect a wide range of processes in the brain, altering neurotransmission, electrophysiological activity, metabolism, cell division, and death. These actions are mediated by corticosteroid receptors (glucocorticoid and mineralocorticoid) that modify transcriptional activity of target genes. The amount of steroid available to activate these receptors is not only dependent on the circulating levels but also on pre-receptor metabolism of glucocorticoids occurring intracellularly. This metabolism is carried out by the enzymes 11beta-hydroxysteroid dehydrogenases (11beta-HSDs). There are two distinct isozymes, the products of distantly related genes. 11beta-HSD type 2 inactivates glucocorticoids to its inert 11-keto derivative, while 11alpha-HSD type 1 elevates intracellular glucocorticoid levels by regenerating active glucocorticoids from circulating 11-dehydrocorticosterone or cortisone. This review highlights the important and very different roles the two enzymes play in the brain, outlining recent results obtained from studying mice with a targeted gene deletion in the 11beta-HSD1 or 11beta-HSD2 genes.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed1997

11 beta-Hydroxysteroid dehydrogenase and its role in the syndrome of apparent mineralocorticoid excess.

Aldosterone, the most important mineralocorticoid, regulates electrolyte excretion and intravascular volume mainly through its effects on renal distal tubules and cortical collecting ducts, where it acts to increase sodium resorption from and potassium excretion into the urine. Excess secretion of aldosterone or other mineralocorticoids, or abnormal sensitivity to mineralocorticoids, may results in hypokalemia, suppressed plasma renin activity, and hypertension. The syndrome of apparent mineralocorticoid excess (AME) is an inherited form of hypertension in which 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) is defective. This enzyme converts cortisol to its inactive metabolite, cortisone. Because mineralocorticoid receptors themselves have similar affinities for cortisol and aldosterone, it is hypothesized that the deficiency allows these receptors to be occupied by cortisol, which normally circulates at levels far higher than those of aldosterone. We cloned cDNA and genes encoding two isozymes of 11 beta-HSD. The liver (L) or type 1 isozyme has relatively low affinity for steroids, is expressed at high levels in the liver but poorly in the kidney, and is not defective in AME. The kidney (K) or type 2 isozyme has high steroid affinity and is expressed at high levels in the kidney and placenta. Mutations in the gene for the latter isozyme have been detected in all kindreds with AME. Moreover, the in vitro enzymatic activity conferred by each mutation is strongly correlated with the ratio of cortisol to cortisone metabolites in the urine [tetrahydrocortisone (THF) +allo-THF]/THE. This suggests that the biochemical phenotype of AME is largely determined by genotype.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2002

Antenatal dexamethasone: effect on ovine placental 11beta-hydroxysteroid dehydrogenase type 2 expression and fetal growth.

Antenatal glucocorticoids are routinely given to women at risk for preterm delivery. The fetus is protected from excessive glucocorticoids by the placental enzyme 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD-2), which catalyzes the conversion of cortisol to its biologically inactive metabolite, cortisone. We examined the effects of antenatal dexamethasone on the expression of placental 11beta-HSD-2 in fetal sheep. Ewes were randomized to receive repeated or single courses of dexamethasone or placebo beginning at 76-78 or 104-106 d of gestation, respectively. In the single course group, the ewes received dexamethasone (6 mg, n = 7) or placebo (n = 6) as four intramuscular injections over 48 h up to 18 h before placental harvest. In the repeated course group, the ewes received the same treatment (dexamethasone, n = 10, or placebo, n = 9) once a week for 5 consecutive weeks starting at 76-78 d of gestation. Placental harvest occurred at 106-108 d of gestation in the four groups. By semi-quantitative RT-PCR, we found that placental 11beta-HSD-2 expression was lower in the fetuses of ewes exposed to a single course of dexamethasone than placebo (p < 0.05). Placental 11beta-HSD-2 expression did not differ significantly between fetuses of ewes treated with repeated courses of dexamethasone compared with placebo, or a single course of dexamethasone. Fetuses of dexamethasone treated ewes weighed less than those of placebo treated ewes (ANOVA, main effects for dexamethasone versus placebo treatment: F = 14.5, p = 0.007). Fetuses of ewes exposed to repeated courses of dexamethasone weighed less than those of ewes exposed to placebo or a single course of dexamethasone (p < 0.05). We conclude that maternal antenatal dexamethasone treatment reduces placental 11beta-HSD-2 expression and fetal weight at mid-gestation in the ovine pregnancy.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗
PubMed2003

11beta-hydroxysteroid dehydrogenase complementary deoxyribonucleic acid in rainbow trout: cloning, sites of expression, and seasonal changes in gonads.

11beta-Hydroxysteroid dehydrogenases (11beta-HSDs) are important steroidogenic enzymes for catalyzing the interconversion of active glucocorticoid (cortisol and corticosterone) and inert 11-keto forms (cortisone and 11-dehydrocorticosterone) in mammals. In teleosts, 11beta-HSD also plays a role in the production of the predominant androgen, 11-ketotestosterone, in male fish. In this study we cloned cDNAs encoding rainbow trout 11beta-HSD (rt11beta-HSD) from testes and head kidney. The predicted amino acid sequence, hydrophobicity analysis, and transient transfection assays with rt11beta-HSD in HEK293 cells showed that rt11beta-HSD is a homolog of mammalian 11beta-HSD type 2. rt11beta-HSD transcripts are present in steroidogenic tissues and in a number of other tissues. Strong in situ hybridization signals for rt11beta-HSD transcripts were found in Leydig cells of testes, in thecal cells of the early vitellogenic ovarian follicles, and in thecal and granulosa cells of the midvitellogenic and postovulatory follicles. Weaker signals were also found in head kidney interrenal cells from juvenile rainbow trout. Seasonal changes in rt11beta-HSD transcripts in testes showed a pattern similar to that of stress-induced serum cortisol levels, but not to serum androgen levels. High levels of rt11beta-HSD transcripts were found in ovarian follicles from late vitellogenesis through ovulation. These results raise the possibility of a role for rt11beta-HSD in the protection of developing gonads from the inhibitory effects of stress-induced cortisol.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed2003

Early inflammatory responses in experimental cardiac hypertrophy and fibrosis: effects of 11 beta-hydroxysteroid dehydrogenase inactivation.

In epithelial tissues such as kidney, mineralocorticoid receptors (MR) are protected against glucocorticoid occupancy by the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) type 2. If the enzyme is congenitally inactive, or blocked by carbenoxolone, physiologic glucocorticoids act as MR agonists in such tissues. In most nonepithelial tissues, including cardiomyocytes, 11 beta HSD2 is expressed at minimal levels; in these tissues physiologic glucocorticoids act as MR antagonists, with the basis for this tissue selectivity currently unknown. Vascular smooth muscle cells (VSMC) express MR and 11 beta HSD1/2, with 11 beta HSD1 reported to show uncharacteristic oxidase activity, so that VSMC thus constitute a potential physiologic aldosterone target tissue. Because mineralocorticoid/salt administration triggers marked inflammatory responses in coronary vasculature, we reasoned that VSMC (like epithelial) MR may be activated by glucocorticoids if the protective enzyme is blocked. We thus gave uninephrectomized rats 0.9% NaCl solution to drink, and deoxycorticosterone (DOC, as a single 20 mg sc dose) or carbenoxolone (CBX, 2.5 mg/d in the drinking solution). Both DOC and CBX increased systolic blood pressure, heart, and kidney weight, and expression of cyclooxygenase 2, ED-1-positive macrophages, and osteopontin, with effects of both DOC and CBX blocked by the selective MR antagonist eplerenone. These findings suggest that local glucocorticoid excess, reflecting lower VSMC 11 beta HSD1/2 activity may mimic systemic mineralocorticoid excess, and play a direct etiologic role in coronary vascular inflammatory responses under circumstances of a high salt intake.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2003

Obese Zucker rats have reduced mineralocorticoid receptor and 11beta-hydroxysteroid dehydrogenase type 1 expression in hippocampus-implications for dysregulation of the hypothalamic-pituitary-adrenal axis in obesity.

Obese Zucker rats have elevated basal corticosterone levels and an increased stress response suggestive of an increased activity of the hypothalamic-pituitary-adrenal (HPA) axis. We hypothesized that altered central expression of glucocorticoid receptors (GR), mineralocorticoid receptors (MR), and/or 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) contribute to these changes. In brains from young adult male rats, in situ hybridization and Western blotting showed that obese rats had normal hippocampal GR mRNA and protein levels. In contrast, in obese rats, 11betaHSD1 mRNA levels were reduced in a subpopulation of hippocampal cells in the main neuronal layers (by 37-47%, P < 0.05), whereas 11betaHSD1 levels in sparse high-expressing cells did not differ. MR mRNA was decreased in all regions of the hippocampus (by 37-49%, P < 0.05 for CA1-2 and P < 0.01 for dentate gyrus) and in frontal cortex (by 16%, P < 0.05) in obese rats. In whole hippocampal homogenates, however, neither the protein concentration of MR by Western blot nor activity of 11betaHSD1 was measurably different between the phenotypes. To test the functional importance of lower central MR expression, groups of lean and obese rats were given spironolactone before restraint stress. In vehicle-treated animals, obese rats had higher plasma corticosterone levels than lean rats after stress (by ANOVA, P < 0.05). Spironolactone markedly increased the corticosterone response in both groups, but the incremental rise was smaller in the obese rats, so that spironolactone abolished the differences between groups. We conclude that lower levels of MR, but not GR, contribute to the increased HPA activity in the obese Zucker rats and that this seems more influential during stress than in the basal state. This may be exacerbated by impaired local regeneration of corticosterone by 11betaHSD1. These abnormalities could contribute to the subtle changes in the HPA axis in rodent and human obesity.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2005

11{beta}-Hydroxysteroid dehydrogenase 2 in rat leydig cells: its role in blunting glucocorticoid action at physiological levels of substrate.

Corticosterone (CORT) suppresses Leydig cell steroidogenesis by inhibiting the expression of proteins involved in testosterone biosynthesis including steroidogenic acute regulatory protein and steroidogenic enzymes. In most cells, intracellular glucocorticoid levels are controlled by either or both of the two known isoforms of 11beta-hydroxysteroid dehydrogenase (11beta HSD): the nicotinamide adenine dinucleotide phosphate reduced-dependent low-affinity type I 11beta HSD (11beta HSD1) oxidoreductase and the nicotinamide adenine dinucleotide-dependent 11beta HSD2 high-affinity unidirectional oxidase. In Leydig cells, 11beta HSD1 alone may not be sufficient to prevent glucocorticoid-mediated suppression due to its low affinity for CORT at basal concentrations. The high-affinity unidirectional 11beta HSD2, if also present, may be critical for lowering intracellular CORT levels. In the present study, we showed that 11beta HSD2 is present in rat Leydig cells by PCR amplification, immunohistochemical staining, enzyme histochemistry, immunoprecipitation, and Western blotting. Real-time PCR showed a 6-fold enrichment of 11beta HSD2 mRNA in these cells, compared with whole testis and that the amount of 11beta HSD2 message was about 1000-fold lower, compared with 11beta HSD1. Diffuse immunofluorescent staining of 11beta HSD2 protein in the Leydig cell cytoplasm was consistent with its localization in the smooth endoplasm reticulum. 11beta HSD1 or 11beta HSD2 activities were selectively inhibited using antisense methodology: inhibition of 11beta HSD1 lowered reductase activity by 60% and oxidation by 25%, whereas inhibition of 11beta HSD2 alone suppressed oxidase activity by 50%. This shows that the high-affinity, low-capacity 11beta HSD2 isoform, present at only one thousandth the level of the low-affinity isoform may significantly affect the level of CORT. The inhibition of either 11beta HSD1 or 11beta HSD2 significantly lowered testosterone production in the presence of CORT. These data suggest that both types I and II 11beta HSD in Leydig cells play a protective role, opposing the adverse effects of excessive CORT on testosterone production.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed1985

Evidence for independent 11-oxidase and 11-reductase activities of 11 beta-hydroxysteroid dehydrogenase: enzyme latency, phase transitions, and lipid requirements.

Experimental modification of the membrane structure of rat liver microsomes affected the behavior of the 11-oxidase and 11-reductase components of 11 beta-hydroxysteroid dehydrogenase in different ways. 1) The latency of 11-oxidase was released by detergents, phospholipases, or elevated temperature; 11-reductase activity was not increased by these manipulations. 2) 11-Reductase was rapidly inactivated at 25 C and 37 C; 11-oxidase was stable at these temperatures. 3) Arrhenius plots of microsome bound 11-reductase between 5 C and 40 C showed discontinuity at 23 C. Activation energies above and below the critical temperature were 2 kcal and 16 kcal, respectively. Solubilized 11-reductase showed no discontinuity [activation energy (Ea) = 15 kcal]. Ea for 11-oxidase was 15 kcal at all temperatures for membrane bound or solubilized enzyme, with no discontinuities. 4) Phospholipases A2 and C rapidly inactivated 11-reductase. Triton DF-18 regenerated 50% of the reductase activity of phospholipase C-treated microsomes, but had no effect on phospholipase A2-treated microsomes. Phospholipases increased 11-oxidase activity. The independent behavior of corticosteroid 11-oxidase and 11-reductase are consistent with the properties of closely associated, independent enzymes.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1988

Purification and characterization of the corticosteroid 11 beta-dehydrogenase component of the rat liver 11 beta-hydroxysteroid dehydrogenase complex.

We have proposed that 11 beta-hydroxysteroid dehydrogenase is composed of structurally independent units with 11 beta-dehydrogenase and 11-reductase activities. We now report the purification of rat liver 11 beta-dehydrogenase to apparent homogeneity. Starting with microsomes, 800-fold purification was achieved with agarose-NADP affinity chromatography. No 11-reductase accompanied the purification. Homogeneity of 11 beta-dehydrogenase was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino acid end-group analysis and immunoprecipitation. The terminal amino acid was methionine. Monomer mol wt was 34,000. The enzyme was found to be a glycoprotein. A sequence of 40 amino acid units was identified from the amino end. The amino-terminal region was found to be highly nonpolar. Unlike unpurified microsomal 11 beta-dehydrogenase, which showed curvilinear Eadie plots, homogeneous enzyme gave rectilinear plots. Michaelis constants were 1.83 +/- 0.06 microM for corticosterone and 17.3 +/- 2.24 microM for cortisol. First order rate constants were 10 times greater for corticosterone than cortisol, and maximum velocities were similar.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1990

Regulation of 11 beta-hydroxysteroid dehydrogenase activity in the baboon placenta by estrogen.

We have previously shown that the change in transuteroplacental cortisol (F)-cortisone (E) metabolism in vivo from preferential reduction (E to F) at midgestation to oxidation by term (F to E) does not occur in baboons in which the production or action of estrogen have been blocked. Moreover, because the administration of androstenedione (delta 4A) to baboons increased estradiol (E2) production at midgestation and induced a pattern of F-E metabolism similar to that at term, we suggested that estrogen regulates placental F-E interconversion. The present study was designed to ascertain whether estrogen regulates the activity of the placental 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) enzyme catalyzing the oxidation of F to E. Placentas were obtained on day 100 (n = 10) and day 165 (n = 10) of gestation (term = day 184) from untreated baboons, on day 100 from animals (n = 7) treated with delta 4A between days 70-100 of gestation, and on day 165 from animals in which placental estrogen was decreased by fetectomy (n = 5) on day 100 of gestation. Tissue was homogenized in phosphate buffer (pH 7.4) and microsomal fractions (105,000 x g) incubated (37 C; 2 min) in buffer containing 2.7 mM NAD+ and 0.03-1.0 microM [3H]F. Serum concentrations of E2 (nanograms per ml) in untreated baboons on day 100 (0.7 +/- 0.2) were 3-fold lower than those at term, increased (P less than 0.05) by delta 4A treatment (2.4 +/- 0.3), and decreased (0.12 +/- 0.01; P less than 0.05) by fetectomy. The specific activity (picomoles of E per min/mg protein) of placental 11 beta HSD in untreated baboons at midgestation (134 +/- 17) was increased (P less than 0.01) 3-fold by delta 4A treatment. Enzyme activity at term (148 +/- 29) was similar to that at midgestation, but markedly decreased (P less than 0.01) by fetectomy (16 +/- 4). Placental capacity to oxidize F to E (micromoles per min/placenta) in untreated baboons was 3-fold greater (P less than 0.01) at term (88 +/- 15) than at midgestation and was markedly reduced (P less than 0.01) by fetectomy (3 +/- 1). Collectively, these findings indicate that the activity of the placental 11 beta HSD enzyme catalyzing the oxidation of F to E is increased in baboons in which placental estrogen production was elevated at midgestation and decreased in animals when estrogen formation was inhibited by fetectomy.(ABSTRACT TRUNCATED AT 400 WORDS)

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1990

11 beta-hydroxysteroid dehydrogenase bioactivity and messenger RNA expression in rat forebrain: localization in hypothalamus, hippocampus, and cortex.

In peripheral aldosterone target sites (e.g., kidney), 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) metabolizes corticosterone to inactive 11-dehydrocorticosterone and thus protects mineralocorticoid receptors from exposure to corticosterone in vivo. We have investigated whether 11 beta-OHSD could account for the site-specific differences in corticosteroid receptor sensitivity to corticosterone in rat brain. Enzyme activity, estimated as the percentage conversion of [3H]corticosterone to [3H]11-dehydrocorticosterone in the presence of NADP+ (200 microM), was: hippocampus, 55.8 +/- 2.7%; cortex, 52 +/- 3.1%; pituitary; 40 +/- 2%, hypothalamus, 26.1 +/- 1.2%; brain stem, 21.4 +/- 1.7%; and spinal cord, 12.3 +/- 1.8%. Northern blots, using [32P]dCTP-labeled probes from an 11 beta-OHSD cDNA clone derived from rat liver, showed expression of a single mRNA species in all brain areas, of identical size to 11 beta-OHSD mRNA in liver and kidney. Highest expression was found in hippocampus and cortex. In situ hybridization, using [35S]UTP-labeled cRNA probes, localized high mRNA expression to cerebral cortex (particularly parietal cortex, layer IV), hippocampus (highest in CA3), hypothalamic medial preoptic area and arcuate nuclei and anterior pituitary. In conclusion, there is localized 11 beta-OHSD mRNA expression and enzyme bioactivity in rat brain. The distribution of 11 beta-OHSD corresponds to areas of reduced glucocorticoid or mineralocorticoid receptor affinity for corticosterone. Therefore, 11 beta-OHSD may regulate the access of corticosterone to cerebral mineralocorticoid and/or glucocorticoid receptors and thus modulate corticosteroid effects on brain function.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1990

Characterization of 11 beta-hydroxysteroid dehydrogenase gene expression: identification of multiple unique forms of messenger ribonucleic acid in the rat kidney.

The enzyme 11 beta-hydroxysteroid dehydrogenase (11-HSD) appears to be involved in mediating aldosterone specificity of otherwise nonselective type I receptors in mineralocorticoid target tissues. In the present study gene expression of 11-HSD was characterized in various tissues of the rat by use of a complementary DNA probe coding for the rat liver 11-HSD. In the liver, lung, testis, colon, heart, hippocampus, and kidney papilla a single message was observed of length approximately 1700 nucleotides (nt). In the kidney cortex/medulla, however, messenger RNA (mRNA) species were observed at 1900 nt, 1600 nt and 1500 nt, and deadenylation studies showed that the renal 1900 nt species was heterogeneous. Northern blot analysis of 11-HSD mRNA showed low levels of expression in the kidney of the neonate and much higher levels in liver and lung with expression increasing markedly in all three tissues over development. In mature rats, a low salt diet significantly elevated 11-HSD mRNA in the liver but not in other tissues. We interpret these data as evidence for the existence of a family of 11-HSD genes, and consistent with the possibility that the hepatic species may modulate occupancy of type II (classical) glucocorticoid rather than type I receptors.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1991

Regional distribution of 11 beta-hydroxysteroid dehydrogenase in rat brain.

The activity and distribution of 11 beta-hydroxysteroid dehydrogenase in rat brain is described. Oxidation of corticosterone to 11-dehydrocorticosterone was significantly increased by NADP; the reverse reaction was increased by NADPH. Cortisol was a poor substrate. Both 11-dehydrogenase (11-DH) and 11-oxoreductase (11-OR) activities were found in brains of rats from 6 days to adult, and 11-DH and 11-OR activities were positively correlated with each other. Highest enzyme activities were found in pituitary, cerebellum, hippocampus, and cortex. Lower levels were found in the olfactory region, hypothalamus, brain stem, preoptic nucleus, and amygdala. Two antisera to 11-DH, designated 56-125 and 56-126, reacted with a 34K component corresponding in mass to rat liver 11-DH on Western blots. The dominant species of protein in all brain regions reacting with rat liver 11-DH antibody 56-125, was at 26K mol wt. Antiserum 56-126 did not cross-react with the 26K protein. The 26K component was not a 34K degradation product. In each region of the brain, Western blot analysis showed that the 26K band intensity was directly proportional to enzyme activity. However, the 26K protein was devoid of 11-DH activity. All 11-DH and 11-OR activities were associated with the 34K antigen. The data demonstrate the nonuniform distribution of 11-DH in brain tissue. They are consistent with the notion that 11-DH may confer upon brain the ability to control intracellular levels of active glucocorticoids and in this way mediate steroid function within the cell.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1991

11 beta-Hydroxysteroid dehydrogenase activity in the renal target cells of aldosterone.

Aldosterone selectivity in mineralocorticoid target tissues has been suggested to be due to 11 beta-hydroxysteroid dehydrogenase (11-OHSD), which, by inactivating the endogenous glucocorticoids cortisol and corticosterone (CS), would allow aldosterone to bind to the mineralocorticoid receptor that has equal affinity for aldosterone and natural glucocorticoids. However, a recent immunohistochemical study failed to colocalize 11-OHSD and mineralocorticoid receptors in the kidney. The goal of this study was to determine 1) whether metabolism of CS occurs in the renal target cells of aldosterone, i.e. in cortical collecting duct cells, and 2) if it does so, whether this activity is sufficient to reduce intracellular CS levels to allow binding of aldosterone to the mineralocorticoid receptor. Cortical collecting duct cells were isolated by solid phase immunoadsorption, with a cell purity of approximately 98%. Metabolism of CS was studied in both freshly isolated cells and primary cultures grown as monolayers on permeable supports. Freshly isolated cells rapidly converted CS to 11-dehydro-CS, which was the only major metabolite detected. In intact collecting duct cells 11-OHSD had an apparent Km for CS of approximately 60 nM, a value more than 100-fold lower than the Km of 11-OHSD in the rat liver, and a maximum velocity of approximately 1.7 x 10(-14) mol/min.1000 cells. In cultured cells, when [3H]CS was applied to one side of the monolayer, almost all radioactivity on the opposite side was 11-dehydro-CS. The cells were able to almost completely metabolize CS passing through them for up to a concentration of 2.5 x 10(-7) M. Carbenoxolone, an inhibitor of 11-OHSD, reduced CS degradation by 88%. Neither freshly isolated nor cultured collecting duct cells converted [3H]11-dehydro-CS back to CS in a significant amount (less than 1%). These data provide functional evidence for 11-OHSD activity in renal aldosterone target cells and indicate that this enzyme might be a collecting duct-specific isoform of 11-OHSD which can sufficiently reduce intracellular CS concentrations to contribute to the apparent mineralocorticoid selectivity of the collecting duct.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1991

11 beta-hydroxysteroid dehydrogenase in vascular smooth muscle and heart: implications for cardiovascular responses to glucocorticoids.

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) converts the active glucocorticoid corticosterone to inactive 11-dehydrocorticosterone in the rat (or cortisol to cortisone in man), thereby protecting renal mineralocorticoid receptors from corticosterone or cortisol and allowing preferential access for aldosterone. We have previously demonstrated that cortisol-induced cutaneous vasoconstriction in man is potentiated by the 11 beta-OHSD inhibitor glycyrrhetinic acid, suggesting that 11 beta-OHSD may protect vascular corticosteroid receptors. In this study we report quantitation of 11 beta-OHSD bioactivity in homogenates of rat aorta, mesenteric artery, caudal artery, and heart, expressed as the percent in vitro conversion of 3H-corticosterone to 3H-11-dehydrocorticosterone. Nicotinamide adenine dinucleotide phosphate (NADP+)-dependent 11 beta-OHSD activity was found in all of these tissues and was significantly higher in resistance vessels than aorta (P less than 0.05) [without NADP+: caudal artery (4.2 +/- 0.2%) greater than mesenteric artery (2.5 +/- 0.7%) = heart (1.67 +/- 0.2%) greater than aorta (0.79 +/- 0.2%); with 200 microM NADP+: caudal artery (43.9 +/- 2.1%) greater than heart (20.6 +/- 1.0%) = mesenteric artery (17.7 +/- 3.1%) = aorta (11.4 +/- 0.4%); heart greater than aorta]. All of these were lower than renal cortex (29.4 +/- 1.8% without NADP+; 82.4 +/- 0.4% with NADP+; P less than 0.001). 3H-11-dehydrocorticosterone was the major metabolite of 3H-corticosterone (greater than 97% of 3H-corticosterone metabolized). Reduction of 3H-11-dehydrocorticosterone to 3H-corticosterone was not detected in these experiments. We also report localization of 11 beta-OHSD-like immunoreactivity by immunohistochemistry using antisera raised against rat liver 11 beta-OHSD, and of 11 beta-OHSD messenger RNA expression by in situ hybridization using complementary RNA probes transcribed from complementary DNA encoding rat liver 11 beta-OHSD. We found 11 beta-OHSD immunoreactivity and messenger RNA expression in vascular and cardiac smooth muscle cytoplasm but not in endothelium. Thus, 11 beta-OHSD is appropriately sited to modulate access of corticosterone to vascular receptors and could influence vascular resistance, cardiac output and thereby blood pressure.

11-beta-Hydroxysteroid Dehydrogenases↗