Carbenoxolone Disodium Treatment for Canine Pituitary-Dependent Hyperadrenocorticism

Pituitary-dependent hyperadrenocorticism (PDH) is mainly caused by pituitary corticotroph tumors in dogs. A characteristic feature of corticotroph tumors is their resistance to negative feedback by glucocorticoids. In some animal species, including dogs, the aberrant expression of 11β-hydroxysteroid dehydrogenase (11HSD), a cortisol metabolic enzyme, is observed in corticotroph tumors. We previously reported that carbenoxolone (CBX), an inhibitor of 11HSD, suppressed ACTH secretion from the pituitary gland, and decreased cortisol concentrations in healthy dogs. Therefore, the aim of this study was to investigate the therapeutic effects of CBX on dogs with PDH. Six dogs with PDH were treated with 60 to 80 mg/kg/day of CBX for 6 weeks, followed by trilostane, which is a commonly used agent for canine PDH. CBX treatment led to a gradual decrease in both basal and in corticotropic releasing hormone (CRH)-stimulated plasma ACTH concentrations and CRH-stimulated serum cortisol concentrations, without side effects. However, basal and stimulated ACTH and cortisol concentrations remained higher than those of healthy dogs, and clinical symptoms such as polydipsia and polyuria were not ameliorated. After a 2-week wash-out interval, trilostane was administered for 2 weeks. Although basal plasma ACTH concentrations were higher after trilostane treatment than CBX treatment, polydipsia and polyuria resolved in all six dogs. The reason for the lack of improvement in polydipsia and polyuria with CBX treatment is unclear. Other mechanisms, in addition to a partial decrease in ACTH secretion, are likely to be involved. In conclusion, this is the first study to report the in vivo effects of CBX in dogs with PDH. The findings suggest that CBX inhibits ACTH secretion from canine pituitary tumors, resulting in lower cortisol concentrations.     

Keratinocytes synthesize and activate cortisol

The bioavailability of circulating and/or endogenous hydrocortisone (cortisol) in epidermal cells is a key determinant in inflammatory disease and chronic wounds. It is not known, however, whether epidermal cells can regulate tissue cortisol and whether they are capable of producing endogenous glucocorticoids. In the present study, we show by microarray analysis that epidermal cells express mRNAs to all the major enzymes involved in the metabolic chain from cholesterol to cortisol, including cytocrome P450 chain, 11β-hydroxysteroid dehydrogenases (HSD11Bs), adrenocorticotropic hormone (ACTH) receptor (MC2R), and glucocorticoid receptor. The two enzymes mediating activation/deactivation of cortisone to cortisol, namely HSD11B1 and HSD11B2, were expressed at the protein level in cultured keratinocytes as well as human skin samples, as shown by Western blotting and immunohistochemistry, respectively. In functional assays, we show that keratinocytes are not only able to activate cortisone to cortisol in a HSD11B-dependent manner but also silencing of either HSD11B1 or HSD11B2 specifically modulates the bioavailability of the inactive glucocorticoid and the active steroid, respectively. A further key observation was that keratinocytes responded to stimulation with ACTH by a significant increase in the de novo synthesis of cortisol. Taken together, we provide evidence for a novel non-adrenal steroideal system in human keratinocytes.     

Differential actions of metyrapone on the fetal pituitary-adrenal axis in the sheep fetus in late gestation

It is not clear if an increase in intra-adrenal cortisol is required to mediate the actions of adrenocorticotropic hormone (ACTH) on adrenal growth and steroidogenesis during the prepartum stimulation of the fetal pituitary-adrenal axis. We infused metyrapone, a competitive inhibitor of cortisol biosynthesis, into fetal sheep between 125 and 140 days of gestation (term = 147 +/- 3 days) and measured fetal plasma cortisol, 11-desoxycortisol, and ACTH; pituitary pro-opiomelanocortin mRNA and adrenal expression of ACTH receptor (melanocortin type 2 receptor), steroidogenic acute regulatory protein (StAR), 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2), cytochrome P450 cholesterol side-chain cleavage (CYP11A1), cytochrome P450 17-hydroxylase (CYP17), 3beta-hydroxysteroid dehydrogenase, and cytochrome P450 21-hydroxylase mRNA; and StAR protein in the fetal adrenal gland. Plasma ACTH and 11-desoxycortisol concentrations were higher (P < 0.05), whereas plasma cortisol concentrations were not significantly different in metyrapone- compared with vehicle-infused fetuses. The ratio of plasma cortisol to ACTH concentrations was higher (P < 0.0001) between 136 and 140 days than between 120 and 135 days of gestation in both metyrapone- and vehicle-infused fetuses. The combined adrenal weight and adrenocortical thickness were greater (P < 0.001), and cell density was lower (P < 0.01), in the zona fasciculata of adrenals from the metyrapone-infused group. Adrenal StAR mRNA expression was lower (P < 0.05), whereas the levels of mature StAR protein (30 kDa) were higher (P < 0.05), in the metyrapone-infused fetuses. In addition, adrenal mRNA expression of 11betaHSD2, CYP11A1, and CYP17 were higher (P < 0.05) in the metyrapone-infused fetuses. Thus, metyrapone administration may represent a unique model that allows the investigation of dissociation of the relative actions of ACTH and cortisol on fetal adrenal steroidogenesis and growth during late gestation.     

Tissue-Specific Increases in 11β-Hydroxysteroid Dehydrogenase Type 1 in Normal Weight Postmenopausal Women

With age and menopause there is a shift in adipose distribution from gluteo-femoral to abdominal depots in women. Associated with this redistribution of fat are increased risks of type 2 diabetes and cardiovascular disease. Glucocorticoids influence body composition, and 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) which converts inert cortisone to active cortisol is a putative key mediator of metabolic complications in obesity. Increased 11βHSD1 in adipose tissue may contribute to postmenopausal central obesity. We hypothesized that tissue-specific 11βHSD1 gene expression and activity are up-regulated in the older, postmenopausal women compared to young, premenopausal women. Twenty-three pre- and 23 postmenopausal, healthy, normal weight women were recruited. The participants underwent a urine collection, a subcutaneous adipose tissue biopsy and the hepatic 11βHSD1 activity was estimated by the serum cortisol response after an oral dose of cortisone. Urinary (5α-tetrahydrocortisol+5β-tetrahydrocortisol)/tetrahydrocortisone ratios were higher in postmenopausal women versus premenopausal women in luteal phase (P<0.05), indicating an increased whole-body 11βHSD1 activity. Postmenopausal women had higher 11βHSD1 gene expression in subcutaneous fat (P<0.05). Hepatic first pass conversion of oral cortisone to cortisol was also increased in postmenopausal women versus premenopausal women in follicular phase of the menstrual cycle (P<0.01, at 30 min post cortisone ingestion), suggesting higher hepatic 11βHSD1 activity. In conclusion, our results indicate that postmenopausal normal weight women have increased 11βHSD1 activity in adipose tissue and liver. This may contribute to metabolic dysfunctions with menopause and ageing in women.     

Endometrial HSD11B1 and cortisol regeneration in the ovine uterus: effects of pregnancy, interferon tau, and prostaglandins

In ruminants, the elongating conceptus secretes interferon tau (IFNT), the pregnancy recognition signal, and prostaglandins (PGs). Progesterone from the ovary induces prostaglandin synthase two (PTGS2) and hydroxysteroid (11-beta) dehydrogenase 1 (HSD11B1) in the endometrial epithelia, and PTGS2-derived PGs regulate endometrial functions and conceptus elongation. The enzyme HSD11B1 interconverts inactive cortisone and active cortisol. These studies determined the effects of pregnancy, IFNT, and PGs on endometrial HSD11B1 expression and activity in the ovine uterus. Study one found that HSD11B1 activity was present in both the endometrium and conceptus during early pregnancy. In study two, ewes received intrauterine infusions of vehicle as a control (CX) or meloxicam (MEL), a PTGS2 inhibitor, from Days 8 to 14 of pregnancy. Endometrial HSD11B1 activity and cortisol in the uterine lumen were substantially lower in MEL-infused ewes. In study three, cyclic ewes received intrauterine infusions of vehicle as a CX, MEL, recombinant ovine IFNT, or IFNT and MEL. Infusion of IFNT increased endometrial HSD11B1 expression and activity and cortisol in the uterine lumen, and this effect was diminished by coinfusion of MEL. In study four, cyclic ewes were infused with vehicle as a CX, IFNT, PGE2, PGF2 alpha, or PGI2. Infusion of all the PGs and IFNT increased endometrial HSD11B1 expression and activity, and IFNT and PGI2 infusion increased cortisol in the uterine lumen. These studies support the idea that IFNT and PGs from the conceptus regulate endometrial HSD11B1 expression and activity that regenerates bioactive cortisol in the ovine uterus during early pregnancy to influence endometrial functions and conceptus elongation.     

Luteoprotective roles of luteinizing hormone are mediated by not only progesterone production but also glucocorticoid conversion in bovine corpus luteum

Luteinizing hormone (LH) is known as a key regulator of corpus luteum (CL) function, but the luteoprotective mechanisms of LH in the maintenance of bovine CL function are not well understood. The current study investigated if LH increases cell viability and induces cortisol conversion, and if the luteoprotective action of LH is mediated by stimulating the local production and action of progesterone (P4) and/or cortisol. Cultured bovine luteal cells obtained at the mid‐luteal stage (Days 8–12 of the estrous cycle) were treated for 24 hr with LH (10 ng/ml) with/without onapristone (OP, a specific P4 receptor antagonist; 100 µM), cortisone (1 µM), and aminoglutethimide (AGT, a specific inhibitor of cytochrome P450 side‐chain cleavage; 100 µM). LH with and without OP significantly increased the mRNA and protein expressions of 11β‐hydroxysteroid dehydrogenase (HSD11B) 1, but did not affect the mRNA or protein expression of HSD11B2. These treatments also significantly increased HSD11B1 activity. Cell viability was significantly increased by LH alone or by LH in combination with cortisone and OP. LH in combination with OP or AGT significantly decreased cell viability as compared to LH alone. The overall results suggest that LH stimulates not only P4 production but also HSD11B1 expression, thereby increasing the cortisol concentration in the bovine CL, and that LH prevents cell death through these survival pathways. LH may consequently support CL function during the luteal phase in cattle. Mol. Reprod. Dev. 80: 204–211, 2013. © 2013 Wiley Periodicals, Inc.     

Antisense inhibition of 11betahydroxysteroid dehydrogenase type 1 improves diabetes in a novel cortisone-induced diabetic KK mouse model

The inhibition of 11βhydroxysteroid dehydrogenase 1 (11βHSD1), an enzyme that catalyzes the conversion of inactive cortisone to active cortisol, is an attractive target to treat diabetes by suppressing hepatic gluconeogenesis. To test this hypothesis, we developed a novel glucocorticoid-induced diabetic KK mouse model and used 11βHSD1 antisense oligonucleotide (ASO) as an inhibitory tool. KK mice were treated with 25 or 50 mg/kg/day of 11βHSD1 ASO for 28 days. On day 25, cortisone pellets were surgically implanted to induce diabetes. In the ASO-treated mice, plasma blood glucose levels were significantly reduced by up to 54%. In parallel, cortisol and other diabetes endpoints were also significantly reduced. Hepatic 11βHSD1 mRNA was suppressed by up to 84% with a concomitant respective decrease of up to 49% in the expression of PEPCK. The results suggest that inhibition of 11βHSD1 activity reduces the availability of cortisol to activate the glucocorticoid receptor, down regulates gluconeogenesis and thus reduces plasma glucose levels in cortisone-induced diabetic KK mice.     

Marked Cortisol Production by Intracrine ACTH in GIP-Treated Cultured Adrenal Cells in Which the GIP Receptor Was Exogenously Introduced

The ectopic expression of the glucose-dependent insulinotropic polypeptide receptor (GIPR) in the human adrenal gland causes significant hypercortisolemia after ingestion of each meal and leads to Cushing’s syndrome, implying that human GIPR activation is capable of robustly activating adrenal glucocorticoid secretion. In this study, we transiently transfected the human GIPR expression vector into cultured human adrenocortical carcinoma cells (H295R) and treated them with GIP to examine the direct link between GIPR activation and steroidogenesis. Using quantitative RT-PCR assay, we examined gene expression of steroidogenic related proteins, and carried out immunofluorescence analysis to prove that forced GIPR overexpression directly promotes production of steroidogenic enzymes CYP17A1 and CYP21A2 at the single cell level. Immunofluorescence showed that the transfection efficiency of the GIPR gene in H295R cells was approximately 5%, and GIP stimulation enhanced CYP21A2 and CYP17A1 expression in GIPR-introduced H295R cells (H295R-GIPR). Interestingly, these steroidogenic enzymes were also expressed in the GIPR (–) cells adjacent to the GIPR (+) cells. The mRNA levels of a cholesterol transport protein required for all steroidogenesis, StAR, and steroidogenic enzymes, HSD3β2, CYP11A1, CYP21A2, and CYP17A1 increased 1.2-2.1-fold in GIP-stimulated H295R-GIPR cells. These changes were reflected in the culture medium in which 1.5-fold increase in the cortisol concentration was confirmed. Furthermore, the levels of adenocorticotropic hormone (ACTH) receptor and ACTH precursor proopiomelanocortin (POMC) mRNA were upregulated 2- and 1.5-fold, respectively. Immunofluorescence showed that ACTH expression was detected in GIP-stimulated H295R-GIPR cells. An ACTH-receptor antagonist significantly inhibited steroidogenic gene expression and cortisol production. Immunostaining for both CYP17A1 and CYP21A2 was attenuated in cells treated with ACTH receptor antagonists as well as with POMC siRNA. These results demonstrated that GIPR activation promoted production and release of ACTH, and that steroidogenesis is activated by endogenously secreted ACTH following GIP administration, at least in part, in H295R cells.     

The effect of estradiol on output of adrenocorticotropin and prolactin by fetal sheep anterior pituitary cells

We examined the hypothesis that estradiol (E2) would affect fetal anterior pituitary corticotroph and lactotroph function in vitro, and that any effects would be influenced by gestational age. Anterior pituitary cells from fetal sheep at day 129 (n = 4) and at day 139 (n = 5) of gestation were cultured. After 96 h in culture, cells were treated for 18 h with E2 concentrations ranging from 0 to 1000 nM, in the presence or absence of 100 nM of corticotropin-releasing hormone (CRH), cortisol, arginine vasopressin (AVP), or CRH and cortisol, to examine their effects on corticotroph function. Cells were also treated with bromocriptine or increasing concentrations of E2 to study their effects on lactotroph function. Immunoreactive (ir) adrenocorticotropin (ACTH) and prolactin in the culture medium were measured by radioimmunoassay. Levels of cellular pro-opiomelanocortin (POMC) mRNA and prolactin mRNA were determined by in situ hybridization. Immunohistochemistry was used to determine the percentage of cells that were immunopositive for ACTH (corticotrophs) or prolactin (lactotrophs). ACTH output was stimulated by CRH treatment at day 139 but not at day 129 of gestation, and cortisol attenuated this response. ACTH output by cells cultured with 10 nM E2 and 100 nM CRH, at 139 days of gestation, was greater than with CRH alone (p < 0.05). E2 did not affect basal ACTH output or ACTH output with any other treatment or levels of POMC mRNA. Prolactin output was not affected by E2 treatment. Bromocriptine significantly decreased prolactin output but not levels of prolactin mRNA. We conclude that E2 may affect CRH-stimulated fetal sheep pituitary corticotroph function late in gestation, but only within a narrow, physiological range of concentration.     

Estrogen Reduces 11β‐Hydroxysteroid Dehydrogenase Type 1 in Liver and Visceral,but Not Subcutaneous,Adipose Tissue in Rats

Following menopause, body fat is redistributed from peripheral to central depots. This may be linked to the age related decrease in estrogen levels. We hypothesized that estrogen supplementation could counteract this fat redistribution through tissue‐specific modulation of glucocorticoid exposure. We measured fat depot masses and the expression and activity of the glucocorticoid‐activating enzyme 11β‐hydroxysteroid dehydrogenase type 1 (11βHSD1) in fat and liver of ovariectomized female rats treated with or without 17β‐estradiol. 11βHSD1 converts inert cortisone, or 11‐dehydrocorticosterone in rats into active cortisol and corticosterone. Estradiol‐treated rats gained less weight and had significantly lower visceral adipose tissue weight than nontreated rats (P < 0.01); subcutaneous adipose weight was unaltered. In addition, 11βHSD1 activity/expression was downregulated in liver and visceral, but not subcutaneous, fat of estradiol‐treated rats (P < 0.001 for both). This downregulation altered the balance of 11βHSD1 expression and activity between adipose tissue depots, with higher levels in subcutaneous than visceral adipose tissue of estradiol‐treated animals (P < 0.05 for both), opposite the pattern in ovariectomized rats not treated with estradiol (P < 0.001 for mRNA expression). Thus, estrogen modulates fat distribution, at least in part, through effects on tissue‐specific glucocorticoid metabolism, suggesting that estrogen replacement therapy could influence obesity related morbidity in postmenopausal women.     

Cortisol as a mineralocorticoid in human disease

The type 2 isozyme of 11β-hydroxysteroid dehydrogenase inactivates cortisol to cortisone and enables aldosterone to bind to the MR. Congenital deficiency of the enzyme results in cortisol-mediated mineralocorticoid excess and arises because of inactivating mutations in the HSD11B2 gene. Inhibition of the enzyme following licorice or carbenoxolone ingestion results in a similar, though milder phenotype and the enzyme is overwhelmed in ectopic ACTH syndrome. Loss of 11β-HSD2 expression may be important in sodium balance and blood pressure control in some patients with renal disease. Finally, while some studies demonstrate impaired 11β-HSD activity in broader populations of patients with hypertension, further studies are required to clarify the role of 11β-HSD2 in ‘essential’ hypertension.     

Evidence for expression of 11β-hydroxysteroid dehydrogenase type3 (HSD11B3/HSD11B1L) in neonatal pig testis

11β-hydroxysteroid dehydrogenase (HSD11B) catalyzes the interconversion between active and inactive glucocorticoid, and is known to exist as two distinct isozymes: HSD11B1 and HSD11B2. A third HSD11B isozyme, HSD11B1L (SCDR10b), has recently been identified. Human HSD11B1L, which was characterized as a unidirectional NADP⁺-dependent cortisol dehydrogenase, appears to be specifically expressed in the brain. We previously reported that HSD11B1 and abundant HSD11B2 isozymes are expressed in neonatal pig testis and the Km for cortisol of NADP⁺-dependent dehydrogenase activity of testicular microsomes obviously differs from the same activity catalyzed by HSD11B1 from pig liver microsomes. Therefore, we hypothesized that the neonatal pig testis also expresses the third type of HSD11B isozyme, and we herein examined further evidence regarding the expression of HSD11B1L. (1) The inhibitory effects of gossypol and glycyrrhetinic acid on pig testicular microsomal NADP⁺-dependent cortisol dehydrogenase activity was clearly different from that of pig liver microsomes. (2) A highly conserved human HSD11B1L sequence was observed by RT-PCR in a pig testicular cDNA library. (3) mRNA, which contains the amplified sequence, was evaluated by real-time PCR and was most strongly expressed in pig brain, and at almost the same levels in the kidney as in the testis, but at lower levels in the liver. Based on these results, neonatal pig testis appears to express glycyrrhetinic acid-resistant HSD11B1L as a third HSD11B isozyme, and it may play a physiologically important role in cooperation with the abundantly expressed HSD11B2 isozyme in order to prevent Leydig cell apoptosis or GC-mediated suppression of testosterone production induced by high concentrations of activated GC in neonatal pig testis.     

Galanin in pituitary adenomas

Tumor galanin content was measured in extracts from human pituitary adenomas using a specific RIA method for monitoring human galanin. Twenty-two out of twenty-four tumors contained galanin with notably high levels in corticotroph adenomas, varying levels in clinically inactive tumors, and low levels in GH secreting adenomas. Tumor galanin and ACTH contents were closely correlated in all tumors. In four young patients with microadenomas and highly active Mb Cushing tumor galanin was inversely related to tumor volume. The molecular form of tumor galanin, studied with reverse-phase HPLC, was homogeneous with the majority of tumor galanin coeluting with standard human galanin. In the tumors analysed with in situ hybridization there was a good correlation between galanin peptide levels and galanin mRNA expression. In some tumors galanin mRNA and POMC levels coexisted, in others they were essentially in different cell populations. Levels of plasma galanin-LI were not related to tumor galanin concentration, and galanin levels were in the same range in sinus petrosus close to the pituitary venous drainage as in peripheral blood. Corticotrophin releasing hormone injections in two patients caused ACTH, but no detectable galanin release into sinus petrosus. Our results demonstrate that corticotroph, but not GH adenomas, express high levels of galanin, in addition to ACTH, and that in some tumors both polypeptides are synthesised in the same cell population. However, galanin levels in plasma were not influenced by the tumor galanin content.     

Sex steroids and leptin regulate 11beta-hydroxysteroid dehydrogenase I and P450 aromatase expressions in human preadipocytes: Sex specificities

Adipose tissue is an important site of steroid hormone biosynthesis, as type I 11β-hydroxysteroid dehydrogenase (HSD1), the enzyme responsible for the conversion of cortisone into cortisol and the P450 aromatase, the enzyme catalysing androgens aromatization into estrogens, are both expressed in human adipose tissue. In the present report, we have investigated the possibility that sex steroids and leptin could regulate these two enzymes in cultured preadipocytes from men and women intra-abdominal fat depots.

In women preadipocytes, human recombinant leptin down-regulates HSD1 mRNA expression (−58%) and P450 aromatase activity (−26%). Conversely, leptin up-regulates the HSD1 (2.4-fold) and the P450 aromatase (1.6-fold) mRNA expression in men preadipocytes. In women preadipocytes, 17β-estradiol strongly stimulates HSD1 mRNA expression (10-fold) and, in contrast, decreases by half the P450 aromatase expression. In men, 17β-estradiol has no influence on HSD1 expression but up-regulates P450 aromatase mRNA expression (2.4-fold). Finally, androgens increase by a factor of 2.5–5 the mRNA expression of both enzymes in men.

These findings suggest that sex steroids and leptin either increase or decrease local cortisol and estrogens productions in men or in women preadipocytes, respectively. They also indicate that steroid metabolism in adipose tissue is controlled by a coordinated regulation of P450 aromatase and HSD1 expressions. Finally, the important sex-specific differences described herein may also contribute to explain the sexual dimorphism of body fat distribution in humans.     

11Beta-hydroxysteroid dehydrogenase type 2 and the regulation of surfactant protein A by dexamethasone metabolites

Glucocorticoid (GC) metabolism by the 11beta-hydroxysteroid dehydrogenase (HSD) system is an important prereceptor regulator of GC action. The HSD enzymes catalyze the interconversion of the endogenous, biologically active GC cortisol and its inactive 11-dehydro metabolite cortisone. The role of the HSD enzymes in the metabolism of synthetic GCs, such as dexamethasone (Dex), is more complex. The human lung is a classic GC-sensitive organ; however, the roles of the HSD enzymes (HSD1 and HSD2) in the human lung are poorly understood. In the present study, we examined the expression of the HSD enzymes in human adult and fetal lung tissues and the human lung epithelial cell line NCI-H441. We observed that human adult and fetal lung tissues, as well as H441 cells, express HSD2 protein and that it is upregulated by Dex (10(-7) M). By contrast, HSD1 protein was undetectable. We also show that the Dex-mediated regulation of surfactant protein A is attenuated by inhibition of HSD2 activity. Furthermore, we demonstrate that unlike the inactive, 11-dehydro metabolite of cortisol (i.e., cortisone), the 11-dehydro metabolite of Dex, 11-dehydro-Dex, competes for binding to the GC receptor (GR) in human lung epithelial cells and retains GR agonist activity. Together, these data suggest that differences exist in the biological activities of the metabolites of cortisol and Dex.     

The human gene for 11 beta-hydroxysteroid dehydrogenase. Structure, tissue distribution, and chromosomal localization

The Type I (mineralocorticoid) receptor has identical affinities in vitro for cortisol and aldosterone. It has been suggested that the selective role of aldosterone in regulating sodium homeostasis relies on the microsomal enzyme 11 beta-hydroxysteroid dehydrogenase (11-HSD). This enzyme converts cortisol to its inactive metabolite, cortisone, preventing cortisol from binding to the Type I receptor. We have isolated human cDNA clones encoding 11-HSD from a human testis cDNA library by hybridization with a previously isolated rat 11-HSD cDNA clone. The cDNA contains an open reading frame of 876 bases, which predicts a protein of 292 amino acids. The sequence is 77% identical at the amino acid level to rat 11-HSD cDNA. The mRNA is widely expressed, but the level of expression is highest in the liver. Hybridization of the human 11-HSD cDNA to a human-hamster hybrid cell panel localized the single corresponding HSD11 gene to chromosome 1. This gene was isolated from a chromosome 1 specific library using the cDNA as a probe. HSD11 consists of 6 exons and is at least 9 kilobases long. The data developed in this study should be applicable to the study of patients with hypertension due to apparent mineralocorticoid excess, a deficiency in 11-HSD activity.