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PubMed1994

Gestational age dependence of 11 beta-hydroxysteroid dehydrogenase and its relationship to the enzymes of phosphatidylcholine synthesis in lung and liver of fetal rat.

Increase in fetal surfactant synthesis and lung maturity is caused by the glucocorticoidal induction of enzymes required for phosphatidylcholine (PC) synthesis towards the end of gestation. The regulation of gestational age-dependent induction of PC synthesis by glucocorticoids is still unclear. Since 11-beta-hydroxysteroid dehydrogenase (11 beta-HSD) activity and its metabolising capacity for glucocorticoids have been suggested to play a central role in this regulation, we measured the gestational age-dependent changes in 11 beta-HSD and PC synthesizing enzymes in lung and liver of fetal rat. The activity of cholinephosphate cytidyltransferase (CCT; key enzyme in PC synthesis), choline phosphotransferase (CPT) and lysolecithin acyltransferase (LAT) were found to increase gradually in the lung towards the end of gestation, reached peak values at term followed by a decrease of activity reaching finally adult levels. Only CK activity exhibited constant levels until term followed by a slight increase after the birth. In comparison with the lung, the liver enzymes followed a similar pattern, but at a higher rate of activity except for CCT which was higher in the lung. The activity of 11 beta-HSD in fetal lung microsomes was detectable from day 20 and increased towards the end of gestation in the lung and liver of the rat. Oxidase activity was always found to exceed the reductase activity. The activity of 11 beta-HSD continued to increase after delivery and reached peak levels in adult animals in both organs. In order to test the hypothesis, whether 11 beta-HSD activity and PC synthesis are induced by increasing endogenous glucocorticoidal levels, we examined on day 19 of gestation the effect of dexamethasone (DEXA) on enzymatic activities (11 beta-HSD, CCT) and on [14C]choline incorporation in phosphatidylcholine in fetal lung organoid cultures. Additionally, changes in CCT activity in fetal lungs after maternal administration of DEXA were measured. DEXA accelerated 11 beta-HSD and CCT activities as well as [14C]choline incorporation. We conclude, that endogenous glucocorticoids induce PC synthesis as well as 11 beta-HSD activity in lung and liver of the fetal rat. Fetal PC synthesis is not altered by increasing 11 beta-HSD levels, because the increase of free serum corticosterone levels apparently exceeds the metabolising capacity of 11 beta-HSD towards term.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1992

Human hepatic 3 alpha-hydroxysteroid dehydrogenase: possible identity with human hepatic chlordecone reductase.

3 alpha-Hydroxysteroid dehydrogenase is a cytosolic, monomeric, NADPH-dependent oxidoreductase which reduces 3-keto-5-dihydrosteroids to their tetrahydro products. We present here the first partial amino acid sequence data for the human liver enzyme and show these sequences to be identical to the deduced amino acid sequence for human hepatic chlordecone reductase. In addition, these two enzymes exhibit similar substrate and cofactor specificities and immunological reactivity. The results suggest that the natural substrates for chlordecone reductase are 3-keto-5-dihydrosteroids and that these two proteins may be identical.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Tyr-179 and Lys-183 are essential for enzymatic activity of 11 beta-hydroxysteroid dehydrogenase.

Tyr-179 and Lys-183 are likely to be functionally important residues in 11 beta-hydroxysteroid dehydrogenase, as these amino acids are absolutely conserved in all members of the "short chain dehydrogenase" family. We modified these residues by site-directed mutagenesis of rat cDNA and transfected these constructs into CHO cells. A highly but not absolutely conserved residue, Asp-110, was also studied. Mutation of Tyr-179 to Phe or Ser completely abolished enzymatic activity (interconversion of corticosterone and 11-dehydrocorticosterone), as did Lys-183-->Arg. Asp-110-->Asn affected activity only mildly. Tyr-179 and Lys-183 may be directly involved in the catalytic function of this class of enzymes.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1992

Hormonal regulation of 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase in rat liver cytosol.

In rat liver, dihydrodiol dehydrogenase and 3 alpha-hydroxysteroid dehydrogenase activities are catalyzed by the same protein. This study shows that estrogen and growth hormone can induce the enzyme in hypophysectomized rats. This implies that estrogen can exert an effect on hepatic steroid and carcinogen metabolism in the absence of the anterior pituitary.

3-Hydroxysteroid Dehydrogenases↗
PubMed1994

11 beta-hydroxysteroid dehydrogenase mediates reductive metabolism of xenobiotic carbonyl compounds.

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) is considered to confer mineralocorticoid specificity on the non-selective Type I adrenocorticoid receptor by converting active 11-hydroxyglucocorticoids to receptor-inactive 11-oxo metabolites, in mineralocorticoid target tissues like the kidney. However, 11 beta-HSD is also present in the liver, where it may regulate steroid exposure to the glucocorticoid Type II receptor. Because of the much higher activities compared to that in kidney, liver 11 beta-HSD possibly has additional functions besides the metabolism of glucocorticoids. In the present investigation we have isolated 11 beta-HSD from mouse liver microsomes and demonstrate that the homogeneously purified enzyme is also capable of catalyzing the reductive metabolism of xenobiotic carbonyl compounds such as metyrapone, p-nitroacetophenone and p-nitrobenzaldehyde. Enzyme kinetic studies revealed that, in addition to NADP+, mouse liver 11 beta-HSD also accepts NAD+ as cosubstrate for glucocorticoid 11 beta-dehydrogenation. NADH as cosubstrate for 11-oxoreduction plays only a minor role compared to that with NADPH, a fact which is also true for xenobiotic carbonyl reduction. Inhibition experiments revealed strong sensitivity of xenobiotic carbonyl reduction to glucocorticoids. The competitive nature of this inhibition suggests that both glucocorticoids and xenobiotic carbonyl substances bind to the same catalytically active site of 11 beta-HSD. High enzyme activities were also found in microsomal fractions of the ovary and adrenal gland but, although expressing considerable glucocorticoid 11-dehydrogenation activity (one third that of liver), almost no carbonyl reduction was detectable in kidney microsomes. Immunoblot analysis with polyclonal antibodies directed against the liver 11 beta-HSD did not yield an immunological crossreaction in the same tissues. In conclusion, corresponding to the cytosolic aldo-keto reductases, microsomal 11 beta-HSD of liver may be considered to play a role in the phase I biotransformation of pharmacologically relevant carbonyl substances as well as protecting organisms against toxic carbonyl compounds by converting them to less lipophilic and more soluble and conjugatable metabolites. Discrepancies in bioactivity together with the lack of response to anti-liver 11 beta-HSD antibodies strongly indicate the existence of distinct forms of 11 beta-HSD to be present in kidney, adrenal gland and ovary. The ability of xenobiotic carbonyl reduction might be another distinguishing feature among the various 11 beta-HSD isozymes.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1982

On the presence and regulation of 3 alpha-hydroxysteroid dehydrogenase in the adult rat ovary.

The presence of 3 alpha-hydroxysteroid dehydrogenase activity in adult rat ovaries was assessed by direct measurement of the conversion of dihydrotestosterone to 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol). This enzyme was indeed found in this tissue with a high specific activity (414--560 nmol of 3 alpha-diol formed/h/mg protein) when compared to other hormone-dependent tissues. During the 4-day rat estrous cycle, the enzymatic activity was found to fluctuate by approximately 30% with the peak of activity at proestrus and the nadir at estrus. Further evidence for the hormonal regulation of this enzymatic activity was obtained with hypophysectomy and hormone replacement studies. Hypophysectomy resulted in a nearly 50% decrease when activity is expressed per ovary but this treatment had no significant effect on the specific activity (per mg ovary or per mg protein) of the enzyme. Hormone replacement, via polydimethylsiloxane capsules, with estradiol-17 beta resulted in a doubling of ovarian 3 alpha-HSD activity per mg protein but no significant change on a per ovary basis while replacement with testosterone caused a major decrease in activity to 15--30% (depending on the mode by which enzyme activity is expressed) of control hypophysectomized animals. These data thus indicate that this enzyme activity is present in the ovary and that it is regulated by gonadotrophins or gonadotrophin-induced steroids. The potential significance of these observations on follicular development and atresia is discussed.

3-Hydroxysteroid Dehydrogenases↗
PubMed1982

Partial characterization of the cytoplasmic 20 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.149) of the human placenta at term.

The 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSDH) is a key enzyme in human fetal and maternal progesterone metabolism. In this paper, the cytoplasmic 20 alpha-HSDH of human term placenta is partially characterized in vitro. A 14-fold concentration of the 20 alpha-HSDH was prepared by ultracentrifugation and ammonium sulfate precipitation. The apparent Km values for the substrates progesterone (Km: 4.8 x 10(-5) M) and 20 alpha-DHP (Km: 6.2 x 10(-5) M) and for the cofactors NADPH (Km: 1.9 x 10(-4)) and NADH (Km: 2.6 x 10(-4)) were determined. The temperature optimum for the oxidation of 20 alpha-DHP is 40--50 degrees C. The pH optimum for the reduction of progesterone was found to be pH 6.2 and for the oxidation of 20 alpha-DHP pH 6.5. The addition of glycerol (3 M) to the incubation medium inhibited the conversion rate of 20 alpha-HSDH by 70%. No influence of EDTA could be found. Various bivalent metal ions (1--100 mM) showed a dose-dependent inhibition of 20 alpha-HSDH; a complete inhibition was achieved at 100 mM: Cu2+, Zn2+, Cd2+, Fe2+ and Ni2+.

20-Hydroxysteroid Dehydrogenases↗
PubMed1982

Endogenous inhibition of the 20 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.149) in the human term placenta in vitro.

Human placental 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSDH) interconverts progesterone and 20 alpha-dihydroprogesterone (20 alpha-DHP). In this study, an endogenous inhibitor of the cytoplasmic 20 alpha-HSDH isolated from human term placenta is demonstrated. Characterization of the endogenous inhibitor was carried out by adding heat-denatured fractions of the 20 alpha-HSDH enzyme stock solution to the incubations. The aqueous phase of the 20 alpha-HSDH (after diethylether extraction) using 8-fold concentration of the enzyme inhibited the 20 alpha-HSDH activity by 50%. After ultrafiltration of the aqueous phase, this inhibitory effect (50%) was found in the aqueous fraction with a molecular weight above 12,800. No inhibition of the 20 alpha-HSDH was shown using the ether phase or the aqueous ultrafiltrate with a molecular weight below 12,800. The 20 alpha-HSDH was stimulated by human and bovine serum albumins up to 290% and 420% respectively. Bovine serum albumin showed a higher stimulatory effect on the oxidative (420%) than on the reductive (190%) pathway of the 20 alpha-HSDH. Ovalbumin and immunoglobulin G had no effect. The endogenous inhibitor of the cytoplasmic 20 alpha-HSDH isolated from the human term placenta is heat stable (100 degrees C), water soluble, not soluble in diethylether and has a molecular weight above 12,800. The stimulatory effect of serum albumins in 20 alpha-HSDH may be caused by binding and inactivation of the endogenous inhibitor.

20-Hydroxysteroid Dehydrogenases↗
PubMed1982

Estradiol and progesterone receptor concentrations and 17 beta-hydroxysteroid-dehydrogenase activity in estrogen-progestin stimulated endometrium of women with gonadal dysgenesis.

Four hypergonadotrophic women between 25 and 37 years of age with gonadal dysgenesis were treated sequentially with estrogens and a progestin. The hormonal environment induced by this therapy was similar to that of ovulating women, as demonstrated by serum levels of estradiol, endometrial histology and pituitary gonadotropin secretion before and after LH-RH double stimulation. The concentrations of estradiol and progesterone receptors (ER and PR) and the activity of the 17 beta-hydroxysteroid-dehydrogenase (17 beta-HSD) were determined in endometrial curettings obtained from the above patients at 5 different days of their 28-day artificial cycles. The results were correlated to the histology of the endometrium and the serum concentrations of estradiol at the corresponding days of the cycle. The cytoplasmic ER and PR concentrations in the endometrium were 3-6 times higher during the estrogen than progestin phase of the induced endometrial cycle. For the activity of the 17 beta-HSD, the contrary was the case, being 6-10 fold higher during the progestin phase. A 22-day administration of estrogens only did not lead to a rise in enzyme activity or decrease in receptor content as observed under progestin influence after day 14. Since ER and PR concentrations and 17 beta-HSD activities were similar to those in the endometrium of normally ovulating women, these results confirm experimentally the present concept concerning the dependence of the cytoplasmic ER and PR content and 17 beta-HSD activity on female sex hormone action.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1982

20 alpha-Hydroxysteroid dehydrogenase activity in the rat corpus luteum; a quantitative cytochemical study.

A quantitative cytochemical method for the demonstration of 20 alpha-hydroxysteroid dehydrogenase activity (20 alpha-HSD) in the regressing corpora lutea of the adult rat ovary is described. The method employs unfixed tissue sections and relies upon the oxidation of 20 alpha-hydroxy-4-pregnen-3-one (20 alpha-OH-P) with nitro blue tetrazolium as the hydrogen acceptor. The enzyme was dependent upon NADP+ for its activity and was inactive when 20 beta-hydroxy-4-pregnen-3-one (20 beta-OH-P) was used as a substrate. The apparent Km values for 20 alpha-OH-P and NADP+ were 3 x 10(-4) M and 2.5 x 10(-5) M respectively. Inhibition of 20 alpha-HSD activity by steroids was demonstrable at pH 8. Androstenedione was by far the most potent inhibitor, followed by progesterone (the product of the enzyme activity) 17 alpha-hydroxyprogesterone, Compound S and 20 beta-OH-P. At pH 6.8, a pH more favourable to the progesterone leads to 20 alpha-OH-P reaction, only progesterone and 17 alpha-hydroxyprogesterone were inhibitory. Testosterone was without demonstrable effect at either pH.

20-Hydroxysteroid Dehydrogenases↗
PubMed1984

Investigation of factors influencing 11 beta-hydroxysteroid dehydrogenase (EC 1.1.1.146) activity in midgestational human fetal lung monolayer and explant cultures.

We recently suggested that the 11 beta-hydroxysteroid dehydrogenase (11-HSD) activity in midgestational human fetal lung (HFL) cultures comprised at least two enzymes, one oxidative--associated with epithelial cells, the other reductive--related to fibroblast-like cells. In this study, the effects of various hormones on 11-HSD activity were studied by measuring the interconversion of [3H]cortisol and [14C]cortisone. Human chorionic gonadotrophin, placental medium, and low oxygen concentration increased the conversion of cortisone to cortisol while activity in the reverse direction remained unchanged. No effects were seen when adrenocorticotrophin, prolactin, placental lactogen, estrogens, triiodothyronine or oxytocin were added in physiological amounts.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1984

Studies on the developmental pattern of rat ovarian 3 alpha-hydroxysteroid dehydrogenase: inhibition of the postpubertal activity with medroxyprogesterone acetate in vivo.

The developmental pattern of rat ovarian 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) activity was determined with respect to age, vaginal opening, ovarian histology and serum 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol). The enzyme was assayed by the incubation of [3H]dihydrotestosterone with a portion of whole ovarian cytosol in the presence of 5 X 10(-4) M NADPH. Serum levels of 3 alpha-diol declined from 11.1 +/- 1.2 ng/ml on day 22-3.4 +/- 0.3 ng/ml on day 30 (P less than 0.01). There was no significant change in 3 alpha-HSD during that period which fluctuated from 6.0 +/- 4.0 nmol/h/organ on day 22-8.4 +/- 1.9 nmol/h/organ on day 39. A significant increase on day 42 of 21.1 +/- 6.1 nmol/h/organ occurred well after vaginal opening, corpus luteum formation and the presence of ovarian progesterone; the activity plateaued on day 49 at 31.2 +/- 3.7 nmol/h/organ. In an attempt to inhibit the developmental increase in 3 alpha-HSD activity, medroxyprogesterone acetate (MPA), known inhibitor in vitro was administered to three groups of developing rats in vivo. The administration of MPA at doses of 0.1, 1.0 and 10.0 mg/kg to 30 and 36 day did not inhibit activity when assayed on day 44. In 44-day old rats, the administration of MPA failed to inhibit 3 alpha-HSD activity at 24 h (C-21.1 +/- 2.6; 0.1 mg/kg-19.4 +/- 5.5; 1.0 mg/kg-20.7 +/- 3.7; 10.0 mg/kg-21.1 +/- 3.0 nmol/h/organ) yet there was a significant reduction of 3 alpha-HSD activity when assayed at 48 h (C-21.1 +/- 1.5; 01 mg/kg-9.6 +/- 1.3; 1.0 mg/kg-8.5 +/- 1.9; and 10 mg/kg 5.2 +/- 2.0 nmol/h/organ).

3-Hydroxysteroid Dehydrogenases↗
PubMed1985

Purification and characterization of 20 alpha-hydroxysteroid dehydrogenase from bull testis.

20 alpha-Hydroxysteroid dehydrogenase (20 alpha-HSD) from bull testis has been purified to homogeneity and characterized in terms of apparent molecular weight, lack of subunit composition, substrate and cofactor specificity and certain kinetic parameters. The enzyme activity is localized in the 105,000 g supernatant and is stable at 4 degrees C in the presence of glycerol and dithiothreitol. Purification was achieved by ammonium sulfate precipitation followed by affinity chromatography on reactive red 120-agarose and subsequent gel filtration. The apparent molecular weight of the homogeneous enzyme, as determined by gel filtration on Sephacryl S-300 is 34,000. The mobility of the enzyme in sodium dodecyl sulfate (SDS) gel electrophoresis corresponds to a mol. wt of 40,000. These observations indicate that the enzyme is a single-stranded, monomeric polypeptide. The enzyme catalyzes the reduction of the 17-hydroxyprogesterone to 17,20 alpha-dihydroxy-4-pregnene-3-one in the presence of NADPH, the preferred cofactor. Homogeneous 20 alpha-HSD has an SA of 115 mIU/mg, and has been purified 14,000-fold with an overall 68% recovery. It exhibits a pH optimum at 5.6 and appears to be highly specific for 17-hydroxyprogesterone with an apparent Km-value of 7.3 X 10(-5) M. Androstenedione and corticosterone do not serve as substrates under the described experimental conditions. The enzyme does not possess 17 alpha- or 17 beta-HSD activity.

20-Hydroxysteroid Dehydrogenases↗
PubMed1985

Extraction of 11 beta-hydroxysteroid dehydrogenase from rat liver microsomes by detergents.

In these studies our goal was to solubilize the microsomal enzyme, 11 beta-hydroxysteroid dehydrogenase (11-HSD) as the first step in its purification. Enzyme was extracted from rat liver microsomes with representative detergents (Zwittergents, Tritons, modified sterols). Oxidation-reduction (O-R) ratios of extracts varied with detergent used and ranged from 0.18 (CHAPS) to 3.8 (Zwittergent 3-14) relative to a ratio of 1.7 in intact microsomes. All detergents solubilized 11-HSD using lack of sedimentation during high speed centrifugation as criterion. With Triton DF-18 and Triton X-100, optimum extraction of 11-HSD occurred in the detergent-protein ratio range of 0.1 to 0.2 O-R ratios decreased with increased Triton X-100, but were constant as Triton DF-18 was varied. The pH optimum of enzyme extraction was 9 at a detergent-protein ratio of 0.05 and 7.5-8.0 at a ratio of 0.2. Sodium chloride increased enzyme extraction by detergents; in the absence of detergent, salt extracted protein, but not enzyme. In aqueous solution at 0 degrees C or -15 degrees C, microsomal 11-oxidation activity rose within 24 h, then decreased; reductase activity consistently decreased. Oxidation and reduction activities were inversely related in the microsomal bound enzyme. No relationship between these activities appeared in detergent-solubilized enzymes. Possible mechanisms to account for the unexpected behavior of this enzyme are discussed.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1988

Hydroxysteroid dehydrogenase of Cochliobolus lunatus.

Cochliobolus lunatus is known to be able to hydroxylate steroids at position 11 beta. Besides this inducible enzyme, we found a constitutive hydroxysteroid dehydrogenase activity which is strongly regioselective with the highest activity at position 17, and the best substrate was found to be androstenedione. Using different substrates, no such activities were observed at positions 3 or 11. The enzyme is membrane bound and NADH or NADPH dependent. The protoplasts of Cochliobolus lunatus show the same activity as intact cells, which means that the cell wall does not influence the reaction.

17-Hydroxysteroid Dehydrogenases↗
PubMed1988

Steroid metabolism in testes of patients with incomplete masculinization due to androgen insensitivity or 17 beta-hydroxysteroid dehydrogenase deficiency and normally differentiated males.

For purposes of establishing suitable controls in studies of patients with a suspected enzyme deficiency, activities of enzymes involved in the biosynthesis of testosterone were compared in testes of patients with androgen insensitivity syndrome (AIS) and normally differentiated males with carcinoma of the prostate (Ca prostate) or testis (Ca testis). Activities of 17,20-desmolase and of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) were higher in the testes of pre-, peri- or postpubertal patients with AIS than in elderly men (58-80 yr) with Ca prostate. Activities of 17 beta-HSD (reductive direction) and 3 beta-HSD tended to be higher in peri- or postpubertal than in prepubertal patients with AIS. Activity of 3 beta-HSD was low in the patient with Ca testis. In a peripubertal (12 yr) patient with incomplete masculinization due to a severe deficiency of 17 beta-HSD, reductive activity of 17 beta-HSD was very low compared with that of patients with Ca prostate, Ca testis or AIS. In contrast, in testes from the younger sibling (4 yr), in whom the deficiency of 17 beta-HSD was less severe, 17 beta-HSD reduction of dehydroepiandrosterone was as high as that of men with Ca prostate, yet deficient in comparison with that of more closely age-matched patients with AIS. This emphasizes the desirability of using age-matched tissue for control purposes in enzyme studies.

17-Hydroxysteroid Dehydrogenases↗
PubMed1989

Isoelectric focusing analysis of detergent extracted renal 11 beta-hydroxysteroid dehydrogenase.

11 beta-hydroxysteroid dehydrogenase (11-HSD, EC 1.1.1.146) from rat renal cortex microsomes was solubilized using several detergents, the most effective being Zwittergent 3-10 and Triton X-100. The activity ratio oxidation/reduction of the reversible reaction corticosterone in equilibrium 11-dehydrocoticosterone varied depending on the detergent used. We attribute this variation to direct effects of different detergents on enzyme kinetics. In contrast, comparable results obtained with liver 11-HSD have been attributed to the possibility of spatially separated 11-oxidase and 11-reductase activities. In order to test whether renal 11-HSD represents a uniform oxido-reductase as generally assumed, or a dual enzyme system as has been recently proposed an attempt was made to characterize 11-HSD solubilized from renal microsomal fractions using isoelectric focusing (IEF). When 11-HSD was extracted with 1% Triton X-100 (= partially solubilized fraction) a heterogenous peak pattern was obtained. In contrast, IEF of 11-HSD extracted with 10% Triton X-100 (= delipidated fraction) resulted in a single peak at about pH 5.9 with both oxidative and reductive activity at practically identical positions within the gels. From this observation we conclude that the degree of detergent solubilization of a membrane bound protein affects its amphoteric properties and that removal of membranous lipids is a prerequisite for the analysis of its behaviour. Since the more delipidated fraction of 11-HSD revealed only one activity peak the data are compatible with the uniform enzyme concept since oxidative and reductive activities of renal cortical 11-HSD could not be separated.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1990

11 beta-hydroxysteroid dehydrogenase activity in the mammary gland.

Levels of 11 beta-hydroxysteroid dehydrogenase activity in mammary gland homogenates from pregnant and lactating Sprague-Dawley rats were determined by incubation with [3H]corticosterone under standard conditions, followed by thin-layer chromatography of incubated media. Enzyme activity was high in virgin and pregnant rats, but fell soon after parturition, suggesting a possible role for this enzyme in the co-ordinate regulation of glucocorticoid effects on milk protein synthesis.

11-beta-Hydroxysteroid Dehydrogenases↗