Biomedical subjects

C Monder

Publications and source records attributed to C Monder.

At least 55 records · Page 3Linked to original sources

PubMed1990

Corticosteroid 11 beta-dehydrogenase of rat tissues: immunological studies.

Monospecific polyclonal antibodies to purified homogeneous rat liver corticosteroid 11 beta-dehydrogenase were generated in rabbits. The antibodies were immunoprecipitins, but enzyme activity was not completely suppressed in the antigen-antibody complex. Two antibody preparations, 56-125 and 56-126, used to detect 11 beta-dehydrogenase antigen in Western blots, generated different staining patterns for kidney, liver, brain, and heart. Using the two antibodies together, the total number of antibody-reacting components in kidney was three, and that in liver was two. Based on rates of digestion with proteases, the two prominent immunoreactive proteins in kidney appeared to be structurally or conformationally different. A prominent immunostaining component was present in stomach. Tissues that showed immunochemical evidence of 11 beta-dehydrogenase antigen showed corresponding levels of 11 beta-dehydrogenase activity. Most active were liver, testis, kidney, and lung. Lower levels of activity were found in prostate and epididymis, brain, and reproductive tract. We conclude that 11 beta-dehydrogenase is widely distributed in rat organs and is present at low levels with significant exceptions. The data indicate that 11 beta-dehydrogenase may occur in several enzyme forms, and that the distribution of these forms is to some extent tissue specific.

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↗

PubMed1990

Expression of 11 beta-hydroxysteroid dehydrogenase using recombinant vaccinia virus.

Ligand specificity of the type I steroid receptor is apparently conferred by the activity of 11 beta-hydroxysteroid dehydrogenase. To determine the kinetic properties of this enzyme, rat liver cDNA was expressed in cultured cells using recombinant vaccinia virus. Although this enzyme catalyzes only dehydrogenation when purified from rat liver, the recombinant enzyme obtained from cell lysates catalyzed both 11 beta-dehydrogenation of corticosterone to 11-dehydrocorticosterone and the reverse 11-oxoreduction reaction. At pH 8.5, the first order rate constant Kcat/Km for dehydrogenase activity exceeded that for reductase (63 vs. 38 min-1 x 10(-4], whereas the rate constants for the two reactions were nearly equal (48 vs. 47 min-1 x 10(-4] at pH 7.0. These results are consistent with the previously determined pH optima for these activities in liver microsomes. Removal (with glucose-6-phosphate dehydrogenase) of NADP+ produced by the reductase reaction significantly increased reductase activity. Glycyrrhetinic acid, a known inhibitor of the dehydrogenase reaction, also inhibited the reductase reaction at slightly higher concentrations (50% inhibitory concentration, less than 5 nM for dehydrogenase, 10-20 nM for reductase). Partial inhibition of glycosylation with A1-tunicamycin decreased dehydrogenase activity 50% without affecting reductase activity. The data demonstrate that a single polypeptide catalyzes both dehydrogenation and reduction, although the presence of additional enzyme forms catalyzing one or the other activity has not been ruled out.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1990

Metabolism of cortisol in anorexia nervosa.

In patients with anorexia nervosa 24-h mean plasma concentration of cortisol were 0.44 +/- 0.09 mumol/l (normal less than 0.28 mumol/l). Following stimulation by ACTH (1-24) urinary excretion rates of cortisol were stimulated from 0.22 +/- 0.08 to 4.85 +/- 2.78 mumol/24 h. Similarly, plasma concentrations of the glucocorticoid metabolite, tetrahydrocortisone, increased from 23.3 +/- 9.0 to 47.3 +/- 30.2 nmol/l; urinary excretion rates of tetrahydrocortisone increased from 3.61 +/- 0.90 to 8.40 +/- 1.72 mumol/24 h. The relative share of the sulphate, glucuronide and free fractions of tetrahydrocortisone in the patients' urine did not indicate any defect in metabolization of this steroid metabolite. Excretion rates of the four glucocorticoid tetrahydro-metabolites, tetrahydrocortisone, allotetrahydrocortisone, tetrahydrocortisol, and allo-tetrahydrocortisol, expressed as percent of total steroid excretion, were similar in patients with anorexia and in healthy women under basal conditions (24 +/- 6 vs 23 +/- 6%) and during stimulation by ACTH (1-24) (36 +/- 10 vs 45 +/- 6%). The share of the two androgen metabolites, androsterone and etiocholanolone, was 24 +/- 5% of total steroid excretion (basal; healthy women: 27 +/- 8%) and 13 +/- 2% (ACTH stimulation; healthy women: 12 +/- 4%) in patients with anorexia nervosa. Thus, analysis of urinary steroid excretion rates did not indicate a shift in adrenocortical function. The results confirmed enhanced secretion of cortisol in patients with anorexia nervosa under basal conditions and during/following stimulation by ACTH. The ACTH-induced increase in the concentrations of the tetrahydro-glucocorticoid metabolites in urine was less pronounced than that of cortisol.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1989

Cloning and expression of rat cDNA encoding corticosteroid 11 beta-dehydrogenase.

Corticosteroid 11 beta-dehydrogenase (11-DH) catalyzes the conversion of cortisol to the inactive metabolite cortisone. Absence of 11-DH activity leads to a potentially fatal form of childhood hypertension termed apparent mineralocorticoid excess. As a first step in elucidating the molecular basis of this disorder, we isolated and characterized a rat cDNA clone encoding 11-DH. This clone hybridized to a single mRNA species in liver, kidney, and testis RNA but not to RNA from heart. The insert was 1265 base pairs long and included an 861-base pair open reading frame encoding 287 amino acids. A search of sequence databases revealed that 11-DH is identical in about 27% of amino acid residues to ribitol dehydrogenase from Klebsiella and to the product of the nodG gene from the nitrogen-fixing bacterium, Rhizobium meliloti, thus defining a new superfamily of genes encoding dehydrogenases. The 11-DH cDNA was expressed by transfection into Chinese hamster ovary cells under the control of an SV40 promoter. The expressed enzyme mediated both 11 beta-dehydrogenation and the reverse 11-oxoreduction reaction. Southern blot analysis of rat and human DNA suggested that additional genes related to 11-DH exist in both species.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1989

Evidence for kinetically distinct forms of corticosteroid 11 beta-dehydrogenase in rat liver microsomes.

In this paper we have characterized the 11 beta-dehydrogenase component of the 11 beta-hydroxysteroid dehydrogenase complex in rat liver microsomes. This enzyme oxidized cortisol and corticosterone to cortisone and 11-dehydrocorticosterone, respectively. Corticosterone was oxidized 10-20 times faster than cortisol to its 11-oxo product. In freshly isolated microsomes enzyme activity was partially suppressed. Exposure of the microsomes to detergent or to prolonged incubation (24 h) released latent enzyme activity. Latency release was dependent on steroid concentration. The pH-activity profiles of latent and stimulated enzymes differed in shape (concave vs convex) and in pH optimum (pH 10 vs pH 8.5-9.5). Magnitude of latency release was greatest at pH 7. Corticosterone was a potent inhibitor of cortisol oxidation, but cortisol inhibited corticosterone oxidation poorly. With cortisol or corticosterone as substrates, low and high Km species were found. The high Km form represented about 90% of total enzyme activity in untreated microsomes. When latency was released, the low Km form was not detected. Our results suggest that at least two isozymic forms of corticosterone 11 beta-dehydrogenase reside in rat liver microsomes, or that a single enzyme coexists in two kinetically distinguishable forms.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1989

Synthesis of tritium labeled cortoic acids.

A procedure is described for the microsynthesis and purification of the high specific activity tritium labeled cortisol metabolites, 20 alpha- and 20 beta-cortolic acids and 20 alpha- and 20 beta-cortolonic acids.

Cortisone↗

PubMed1989

Corticosteroid 11 beta-dehydrogenase in rat testis.

Corticosteroid 11 beta-dehydrogenase, the enzyme that catalyzes the oxidation of the biologically active steroid cortisol to its inactive metabolite cortisone, is present in testis. Since excess cortisol in men and other mammals and excess corticosterone in rodents cause physiological abnormalities including abnormal testicular function, it was pertinent to study the cellular distribution of 11 beta-dehydrogenase in the testis. Purified antiserum directed against homogeneous rat 11 beta-dehydrogenase was used to localize the enzyme in the developing rat testis. With immunofluorescence, the enzyme was not detectable in fetal testis or in the testis of young male rats until the 26th day of development. A few interstitial cells were stained in the testis of 26-day-old animals. In the testis of 31-day-old rats many cells in the interstitium were positive. In adult animals the entire interstitial region displayed bright fluorescence. Depleting animals of germ cells did not abolish the fluorescence. The appearance of this enzyme correlates temporally with the postnatal increase in Leydig cell number and the developmental rise in serum testosterone. We suggest that 11 beta-dehydrogenase of Leydig cells protects the testis from the deleterious effects of cortisol.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1989

Licorice inhibits corticosteroid 11 beta-dehydrogenase of rat kidney and liver: in vivo and in vitro studies.

In humans, glycyrrhetinic acid (GE), the active pharmacological ingredient of licorice, produces symptoms resembling those caused by excess mineralocorticoid secretion. We are proposing that 11 beta-dehydrogenase inhibition, and not intrinsic mineralocorticoid activity, is the primary mechanism of licorice induced pseudoaldosteronism. Glycyrrhizic acid (glycyrrhetinic acid glucuronide), when given orally to rats, partially inhibited renal 11 beta-dehydrogenase. In rats treated with dexamethasone before glycyrrhizic acid administration there was similar enzyme inhibition, suggesting that antimineralocorticoid effects of dexamethasone in licorice excess states are not mediated through a direct effect on 11 beta-dehydrogenase activity. Dispersed renal proximal tubular preparations, kidney homogenates, and microsomes readily converted corticosterone to 11-dehydrocorticosterone. GE and its synthetic analog carbenoxolone inhibited the conversion in these systems in a dose-dependent manner. Corticosteroid 11-oxoreductase, which was present in kidney homogenates at a level 10-20% that of 11 beta-dehydrogenase was not inhibited by any of the agents. With homogenate and microsomes, the Ki of GE was about 10(-9)-10(-8) M; with intact tubules, the Ki of GE was about 10(-5)-10(-6) M. It is suggested that a permeability barrier slows the entry of GE into the tubule cells. We conclude that the effects of licorice on corticosteroid metabolism in the kidney are based on its inhibition of 11 beta-dehydrogenase. Our data, supplemented by published evidence, is inconsistent with the conclusion that interaction with mineralocorticoid receptors accounts for the pharmacological effects of GE.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1989

The intrarenal localization of mineralocorticoid receptors and 11 beta-dehydrogenase: immunocytochemical studies.

The 11 beta-dehydrogenase (11-DH) component of the microsomal enzyme complex, 11 beta-hydroxysteroid dehydrogenase, has been postulated to be the specificity-conferring mechanism for the renal type I receptor. To this end, the distribution of 11-DH and the type I receptor was studied in rat kidney by immunocytochemistry. 11-DH-like immunostaining (LI) was found in Bouin's fixed tissue, in both nuclear and cytoplasmic components of some cells of the juxtamedullary proximal convoluted tubules, and in interstitial cells of the papillary medulla. In addition, weak staining was seen in superficial proximal convoluted tubules in paraformaldehyde-fixed tissue. Type I receptor-LI was found in distal convoluted tubules, connecting pieces, and initial cortical collecting tubules of the superficial cortex. Since colocalization of the enzyme and receptor was not demonstrated, the action of 11-DH on type I receptor specificity would, thus, appear to be paracrine rather than autocrine.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1988

Localisation of 11 beta-hydroxysteroid dehydrogenase--tissue specific protector of the mineralocorticoid receptor.

In vitro the mineralocorticoid receptor is non-specific and does not distinguish between aldosterone and cortisol. In vivo certain tissues with this receptor are aldosterone selective (eg, kidney and parotid) whereas others with the same receptor are not (eg, hippocampus and heart). Experiments in rats showed that 11 beta-hydroxysteroid dehydrogenase (which converts cortisol to cortisone in man and corticosterone to 11-dehydrocorticosterone in the rat) was much more highly concentrated in aldosterone-selective tissues than in non-selective tissues. The localisation in the selective tissues was such that the enzyme could act as a paracrine or possibly an autocrine mechanism protecting the receptor from exposure to corticosterone. Autoradiographic studies showed that protection is lost when the enzyme is inhibited; 3H-corticosterone and 3H-aldosterone were bound to similar sites. These findings seem to explain why sodium retention, hypokalaemia, and hypertension develop in subjects with congenital deficiency of 11 beta-OHSD and those in whom the enzyme has been inhibited by liquorice.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1988

In vitro metabolism of 7 alpha-methyl-19-nortestosterone by rat liver, prostate, and epididymis.

The in vitro metabolism of 7 alpha-methyl-19-nortestosterone (7 alpha-methyl-3-oxo-estr-4-ene-17 beta-ol) was investigated in male rat liver, ventral prostate, and epididymis. Three metabolites were recovered from the liver incubation: 7 alpha-methyl-estr-4-ene-3,17-dione, 7 alpha-methyl-5 beta-estrane-3,17 beta-diol, and 7 alpha-methyl-3-oxo-estr-4-ene-16,17 beta-diol, whereas prostate and epididymis did not perceptibly metabolize the steroid. The kinetics of metabolism in liver differed significantly from those of testosterone or 19-nortestosterone. About 85% of the 7 alpha-methyl-19-nortestosterone added was recovered at the end of 30 min of incubation. We conclude that the androgenic potency of 7-alpha-methyl-19-nortestosterone is not dependent on its further conversion to 5 alpha-dihydro-metabolites.

Animals↗

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↗

PubMed1986

An improved procedure for the efficient injection of radioactive steroids into mouse embryos.

Retention of 3H-moxestrol in mouse fetuses after transmaternal, intrafetal, and intraplacental injection were compared. Direct injection into the allantoic placenta resulted in greater retention of radioactivity by the fetus than the other modes of administration between 12 and 16 days of gestation. By this same criterion, intrafetal injection was best for older fetuses. Maternal injection was the least efficient way to transfer 3H-moxestrol to the fetus.

Allantois↗

PubMed1986

Estrogen and progesterone receptors in the organs of prenatal cynomolgus monkey and laboratory mouse.

The estrogen and progesterone receptors of several organs of the prenatal cynomolgus macaque and the fetal mouse were studied using a combination of the dextran-coated charcoal technique and high-performance liquid chromatography. This procedure permitted the concurrent measurement of both receptors in minute amounts of tissue. Estrogen receptors, but not progesterone receptors, were found in the fetal monkey and mouse uteri. No estrogen or progesterone receptors were detected in the lungs, liver, kidney, heart, brain, adrenal gland, or limbs of mouse or monkey fetuses. The nonspecific binding of radioactive ORG-2058 was not displaced by unlabeled progesterone, 17 alpha-hydroxyprogesterone caproate, or ORG-2058. Because the steroid receptors that are indispensable mediators of steroid hormone action were absent from the nonreproductive tissues, prenatal development of these organs and tissues cannot be adversely influenced by exposure to estradiol, progesterone, or their synthetic analogues.

17 alpha-Hydroxyprogesterone Caproate↗

PubMed1986

11 beta,20-dihydroxy-3-oxopregna-4,17(20)-dien-21-al: an intermediate in the biological 17-dehydroxylation of cortisol.

The role of 11 beta,20-dihydroxy-3-oxopregna-4,17(20)-dien-21-al (F enol aldehyde) as an intermediate in the biological conversion of cortisol to a 17-deoxy-21-oic acid was studied in vitro with mouse liver as the source of enzyme. The substrate, [1,2-3H]F enol aldehyde, was synthesized and found to contain cis and trans isomeric forms in a ratio of approximately 3:1. Tritium labeled F enol aldehyde was incubated with mouse liver homogenates. The metabolic products were analyzed by TLC and HPLC. 11 beta,20-Dihydroxy-3-oxopregna-4-en-21-oic acid, a 17-deoxy-21-oic acid, was identified as a quantitatively significant metabolite of the cis isomer. Metabolic conversion of the trans isomer to acid metabolites did not occur. The results are consistent with our hypothesis that the metabolic 17-dehydroxylation of cortisol requires an enol aldehyde intermediate and indicate that the conversion of the enol aldehyde to hydroxy acid is stereospecific.

Animals↗

PubMed1986

The syndrome of apparent mineralocorticoid excess: its association with 11 beta-dehydrogenase and 5 beta-reductase deficiency and some consequences for corticosteroid metabolism.

We describe the metabolism of cortisol (F) in three children, two of them siblings, with apparent mineralocorticoid excess (AME). As with prior patients with AME, oxidation of F to cortisone (E) was impaired, but reduction of E to F was not. We propose that this metabolic defect is caused by deficient 11-dehydrogenase associated with unimpaired 11-reductase. The following supporting observations were made: urinary C21 11-hydroxy metabolites exceeded C21 11-oxo metabolites: ratio of urinary cortols to cortolones, 6.6 +/- 2.8 (+/- SD; normal, 0.47); tetrahydrocortisol (THF) and alloTHF to tetrahydrocortisone, 14.6 +/- 5.6 (normal, approximately 1); normal subjects oxidized [11 alpha-3H]F with transfer of 3H to water; the patients did not; 11-hydroxy, but not 11-oxo, C19 steroids were excreted into the urine; and fibroblasts from patients had 5 times more 11-reductase activity than normal subjects, though fibroblasts from neither group had 11-dehydrogenase activity. Other defects of cortisol metabolism not directly associated with 11-dehydrogenase deficiency were found: impaired conversion of tetrahydro to hexahydro neutral steroids, indicating defective reductive metabolism of the side chain; depressed F production rate and increased half-life of circulating F, resulting in normal blood levels of F; increased excretion of unconjugated F metabolites; and decreased excretion of THF relative to alloTHF, consistent with a 5 beta-reductase defect. Excretion of acidic metabolites of F (cortoic acids) was within the normal range. However, little or no 20 beta-hydroxy acids were excreted, while the level of urinary 20 alpha-hydroxy acids was increased. The 11-hydroxy to 11-oxo ratio of acid metabolites was similar to values in normal subjects. The proportion of cortoic acids relative to neutral hexahydro metabolites was increased (0.37 to 1.27 in patients; 22 in normal subjects). We conclude that children with AME have multiple defects in the conversion of F to neutral metabolites, while metabolism to cortoic acids was less extensively affected. How the defects in cortisol metabolism and the symptoms of AME are related remains to be determined.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1985

Comparison of the distribution kinetics and metabolism to acid end-products of corticosterone and 11-deoxycorticosterone in BALB/c mice.

The conversion of [4 14C]corticosterone[( 14C]B) and 11-deoxy-[1,2-3H]corticosterone [( 3H]DOC) to steroidal carboxylic acids was studied in the BALB/c mouse. There was rapid and preferential excretion of [3H]DOC metabolites into the gastrointestinal tract. Excretion of 14C through the kidney was higher than 3H excretion. Within minutes of intraperitoneal injection, levels of 3H and 14C in most organs reached their maximal levels and subsequently decreased in an exponential pattern. The majority of the organs took up 14C to a greater extent than 3H. Using tissue blood ratio of tracer (T/B) as criterion, it was found that liver, gall bladder, intestine, and kidney concentrated 3H and 14C-labeled steroid from blood. T/B for 3H exceeded that for 14C in the gastrointestinal tract. Abdominal fat preferentially took up [3H]DOC tracer, whereas [14C]B tracer was not taken up by this tissue. T/B was less than 1 for 3H and 14C in heart, thymus, spleen, brain, skeletal muscle and skin. In these organs uptake of B and its metabolites was greater than that of DOC and its metabolites. In liver, [14C]B and [3H]DOC were converted to carboxylic acid metabolites which accumulated in the intestine. The most abundant acid was 11 beta,20 alpha-dihydroxy-3-oxo-pregn-4-en-21-oic acid from B. The acid metabolites of DOC were not identified. For both steroids, acids were major metabolic end-products.

Animals↗