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V Luu-The

Publications and source records attributed to V Luu-The.

At least 127 records · Page 7Linked to original sources
PubMed1991

Evidence for distinct dehydrogenase and isomerase sites within a single 3 beta-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase protein.

Complementary DNA encoding human 3 beta-hydroxysteroid dehydrogenase/5-ene-4-ene isomerase (3 beta-HSD) has been expressed in transfected GH4C1 with use of the cytomegalovirus promoter. The activity of the expressed protein clearly shows that both dehydrogenase and isomerase enzymatic activities are present within a single protein. However, such findings do not indicate whether the two activities reside within one or two closely related catalytic sites. With use of [3H]-5-androstenedione, the intermediate compound in dehydroepiandrosterone (DHEA) transformation into 4-androstenedione by 3 beta-HSD, the present study shows that 4MA (N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxamide) and its analogues inhibit DHEA oxidation competitively while they exert a noncompetitive inhibition of the isomerization of 5-androstenedione to 4-androstenedione with an approximately 1000-fold higher Ki value. The present results thus strongly suggest that dehydrogenase and isomerase activities are present at separate sites on the 3 beta-HSD protein. In addition, using 5 alpha-dihydrotestosterone (DHT) and 5 alpha-androstane-3 beta, 17 beta-diol as substrates for dehydrogenase activity only, we have found that dehydrogenase activity is reversibly and competitively inhibited by 4MA. Such data suggest that the irreversible step in the transformation of DHEA to 4-androstenedione is due to a separate site possessing isomerase activity that converts the 5-ene-3-keto to a much more stable 4-ene-3-keto configuration.

Androgen Antagonists↗
PubMed1991

Characterization of rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase cDNAs and differential tissue-specific expression of the corresponding mRNAs in steroidogenic and peripheral tissues.

The conversion of 3 beta-hydroxy-5-ene steroids by the enzyme complex 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) is an essential step in the biosynthesis of all classes of hormonal steroids. We report the characterization of two types of cDNA clones encoding rat 3 beta-HSD isolated from a rat ovary lambda gt11 cDNA library with a human 3 beta-HSD cDNA probe. Both type I and type II cDNAs encode proteins of 372 amino acids having 94% homology. Transient expression of the type I and the type II 3 beta-HSD cDNAs in HeLa human cervical carcinoma cells reveals that both proteins possess 3 beta-hydroxysteroid dehydrogenase as well as delta 5-delta 4 isomerase activities for both delta 5-pregnene and delta 5-androstene precursors, although the type I 3 beta-HSD protein is more active than the type II. RNA blot analysis using type I 3 beta-HSD cDNA identifies major mRNA transcripts of 1.7 kilobase in rat ovary, testis, and adrenal poly(A)+ RNA. RNase protection assay using type I- and type II-specific cRNA probes revealed the existence of the two corresponding mRNAs in male and female rat adrenals and gonads as well as in female adipose tissue while only type I mRNA is present in male and female kidney. Moreover, in situ hybridization performed using type-specific labeled 24-mer oligonucleotides confirms that type I is the major mRNA species in the ovary and further indicates that both mRNA species have a similar cellular distribution in the ovarian tissue with the highest level of expression found in corpora lutea. Immunoblot analysis using polyclonal antibodies raised against purified human placental 3 beta-HSD identified a single 42-kDa band in rat ovary, testis, and adrenal, which agrees with the calculated molecular masses of 41,911 and 42,150 daltons for the type I and II proteins, respectively. Determination of 3 beta-HSD enzymatic activity using [14C]pregnenolone and [14C]dehydroepiandrosterone as substrates shows that 3 beta-HSD activity is present not only in the gonads and adrenals of animals of both sexes, but also in many peripheral tissues including adipose tissue, mammary gland, kidney, liver, prostate, seminal vesicle, uterus, skin, brain, heart, thymus, pancreas, lung, and spleen. The present data indicate the existence of two mRNAs encoding rat 3 beta-HSD and their differential tissular distribution in both steroidogenic and peripheral tissues.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipose Tissue↗
PubMed1991

Differential inhibition of dehydrogenase and 5-ene----4-ene isomerase activities of purified 3 beta-hydroxysteroid dehydrogenase. Evidence for two distinct sites.

The success in synthesis of [3H]5-androstene-3,17-dione, the intermediate product in the transformation of DHEA to 4-androstenedione by 3 beta-hydroxysteroid dehydrogenase/5-ene----4-ene isomerase (3 beta-HSD) offers the opportunity to determine whether or not the two activities reside in one active site or in two closely related active sites. The finding that N,N-dimethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxamide (4-MA) inhibits competitively and specifically the dehydrogenase activity whereas a non-competitive inhibition type with a Ki value 1000 fold higher was observed for the isomerase activity, indicated that dehydrogenase and isomerase activities belong to separate sites. Using 5 alpha-dihydro-testosterone and 5 alpha-androstane-3 beta, 17 beta-diol, exclusive substrates for dehydrogenase activity, it was shown that dehydrogenase is reversible and strongly inhibited by 4-MA and that thus the irreversible step in the transformation of DHEA to 4-androstenedione is due to the isomerase activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1991

Structure of the human type II 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) gene: adrenal and gonadal specificity.

While classical 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase deficiency (3 beta-HSD) is a known cause of adrenal hyperplasia resulting in ambiguous genitalia and adrenal insufficiency at birth, nonclassical or late-onset 3 beta-HSD deficiency is found in an important proportion of women with androgen excess. We have previously isolated and sequenced the cDNA and gene for the human type I 3 beta-HSD, which represents the main species expressed in the placenta and skin. Recently, we isolated, sequenced, and expressed the functional cDNA encoding type II 3 beta-HSD, which is the predominant 3 beta-HSD expressed in human adrenals and gonads. The present study describes the isolation and complete sequence of the corresponding type II 3 beta-HSD gene, which is the form most likely responsible for human 3 beta-HSD deficiency. The structural gene contains four exons of 57, 231, 165, and 1,214 bp, respectively, separated by introns of 128, 3,383, and 2,162 bp. DNA sequence analysis of the 5'-flanking region reveals the existence of two putative TATA boxes situated 28 and 140 nucleotides upstream from the transcription start site whereas two putative CAAT boxes are located 57 and 38 nucleotides upstream from the TATA boxes, respectively. A restriction fragment length pattern specific for each gene has been characterized. The present findings should provide the tools required for detailed analysis of the molecular basis of 3 beta-HSD deficiency as well as of normal sex steroid biosynthesis.

3-Hydroxysteroid Dehydrogenases↗
PubMed1991

Localization of 17 beta-hydroxysteroid dehydrogenase throughout gestation in human placenta.

17 beta-Hydroxysteroid dehydrogenase (17 beta-HSD) is the enzyme responsible for the formation of all sex steroids in gonadal as well as extragonadal tissues. To obtain more information about the age-specific expression of 17 beta-HSD in the human placenta, we have localized this enzyme by immunocytochemistry at the light microscopic level at different periods of gestation. In the 7- and 9-week-old placenta, immunostaining was detected exclusively in the cytoplasm of the syncytiotrophoblast. Between the tenth and thirteenth weeks of gestation, immunolabeling was also observed in the cytoplasm of the cytotrophoblastic cells, suggesting that these cells could be transiently involved in the biosynthesis of sex steroids. Interestingly, between the fourteenth and twenty-fifth weeks of gestation, 17 beta-HSD was observed in both the cytoplasm and nucleus of the syncytiotrophoblast. The reaction product was much more intense in nuclei than in cytoplasm. During the last trimester of gestation, strong immunocytochemical staining was observed in all the nuclei of the syncytiotrophoblast, the cytoplasm being unstained. The meaning of this nuclear staining for 17 beta-HSD is still unclear and remains to be extensively investigated.

17-Hydroxysteroid Dehydrogenases↗
PubMed1991

Ontogenesis of 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase in the rat adrenal as revealed by immunocytochemistry and in situ hybridization.

The enzyme 3 beta-hydroxy-5-ene-steroid dehydrogenase/5-ene-4-ene isomerase (3 beta-HSD) catalyzes an essential step in the biosynthesis of all classes of active steroids, namely glucocorticoids, mineralocorticoids, progesterone, and sex steroids. To obtain further information on the expression and localization of 3 beta-HSD during development in the rat adrenal, two complementary cytochemical techniques were used: immunocytochemical localization with antibodies against purified human placental 3 beta-HSD, and 3 beta-HSD messenger RNA localization achieved by in situ hybridization with a rat 3 beta-HSD complementary DNA probe. During foetal development, the first detection of 3 beta-HSD messenger RNA was achieved on day 16 by in situ hybridization, the silver grains being located on the cortical cells. Between days 17 and 20, on the other hand, immunostaining became positive in the cytoplasm of the same cortical cells, the capsule being negative by both immunostaining and in situ hybridization. Interestingly, two distinct zones of intensity of 3 beta-HSD localization could be distinguished, namely the highly labeled reticular and fascicular zones and the less positive glomerular zone. This observation coincides with the onset of fetal ACTH secretion on days 17-18 and with accelerated adrenocortical growth and differentiation. After birth and until day 25, strong immunolabeling was observed in the cytoplasm of adrenocortical cells, the glomerular zone being labeled at a lower degree than the remaining cortex. The same localization was obtained by in situ hybridization. This low labeling of the glomerular zone might be related to the low plasma levels of angiotensin II observed in the immature rat. From day 25 after birth, the three zones of the cortex were uniformly labeled and no immunostaining was seen in the medulla or capsule. Similarly, by in situ hybridization, silver grains were located exclusively in the adrenal cortex. The present data suggest that 3 beta-HSD expression could well play a major role in regulating adrenal function during foetal and postnatal development.

3-Hydroxysteroid Dehydrogenases↗
PubMed1991

Structure and expression of a new complementary DNA encoding the almost exclusive 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase in human adrenals and gonads.

The 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta HSD) enzyme catalyzes the oxidation and isomerization of delta 5-3 beta-hydroxysteroid precursors into delta 4-ketosteroids, thus leading to the formation of all classes of steroid hormones. In addition, 3 beta HSD catalyzes the interconversion of 3 beta-hydroxy- and 3-keto-5 alpha-androstane steroids. Clinical observations in patients with 3 beta HSD deficiency as well as our recent data obtained by Southern blot analysis using a human placental 3 beta HSD cDNA (type I) as probe suggested the existence of multiple related 3 beta HSD isoenzymes. We now report the isolation and characterization of a second type of cDNA clone (arbitrarily designated type II) encoding 3 beta HSD after screening of a human adrenal lambda gt22A library. The nucleotide sequence of 1676 basepairs of human 3 beta HSD type II cDNA predicts a protein of 371 amino acids with a calculated molecular mass of 41,921 daltons, which displays 93.5% and 96.2% homology with human placental type I and rhesus macaque ovary 3 beta HSD deduced proteins, respectively. To characterize and compare the kinetic properties of the two isoenzymes, plasmids derived from pCMV and containing type I or type II 3 beta HSD full-length cDNA inserts were transiently expressed in HeLa human cervical carcinoma cells. In vitro incubation with NAD+ and 3H-labeled pregnenolone or dehydroepiandrosterone shows that the type I protein possesses a 3 beta HSD/delta 5-delta 4 isomerase activity higher than type II, with respective Km values of 0.24 vs. 1.2 microM for pregnenolone and 0.18 vs. 1.6 microM for dihydroepiandrosterone, while the specific activity of both types is equivalent. Moreover, incubation in the presence of NADH of homogenates from cells transfected with type I or type II 3 beta HSD indicates that dihydrotestosterone is converted into 5 alpha-androstane-3 beta, 17 beta-diol, with Km values of 0.26 and 2.7 microM, respectively. Ribonuclease protection assay using type I- and type II-specific cRNA probes revealed that type II transcripts are the almost exclusive 3 beta HSD mRNA species in the human adrenal gland, ovary, and testis, while type I transcripts correspond to the almost exclusive 3 beta HSD mRNA species in the placenta and skin and represent the predominantly expressed species in mammary gland tissue. The present data show for the first time that adrenals and gonads express a type of 3 beta HSD isoenzyme that is distinct from the type expressed in the placenta.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Glands↗
PubMed1990

Ontogeny of 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) in human adrenal gland performed by immunocytochemistry.

Human foetal adrenal plays a major role in the synthesis and secretion of steroids which are essential to several physiological events during foetal development. Since 3 beta-hydroxysteroid dehydrogenase 5-ene-4-ene isomerase (3 beta-HSD) is involved in the biosynthesis of all classes of hormonal steroids, namely progesterone, glucocorticoids, mineralocorticoids, androgens and estrogens, knowledge of the ontogeny of 3 beta-HSD should lead to a better understanding of steroidogenesis in the foetal adrenal. Polyclonal antibodies raised against purified human placental 3 beta-HSD were used to localize the enzyme in 22-week, 28-week, and term foetal adrenals as well as in the adrenals of 2-month-, 8-month- and 2-year-old infants. 3 beta-HSD has been identified in the outer cortex, neocortex and zona glomerulosa zone of foetal adrenal, respectively. In 2-month- and 8-month-old infant adrenals, the enzyme was localized in the zona glomerulosa and zone fasciculata while in 2-year-old infants, the immunoreaction was observed also in the zona reticularis, the medulla being devoid of any reaction.

Adrenal Glands↗
PubMed1990

Characterization of human 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase gene and its expression in mammalian cells.

Three beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase (3 beta-HSD) catalyze the oxidative conversion of delta 5-3 beta-hydroxysteroids to the delta 4-3-keto configuration and is therefore essential for the biosynthesis of all classes of hormonal steroids, namely progesterone, glucocorticoids, mineralocorticoids, androgens, and estrogens. Using human 3 beta-HSD cDNA as probe, a human 3 beta-HSD gene was isolated from a lambda-EMBL3 library of leucocyte genomic DNA. A fragment of 3 beta-HSD genomic DNA was also obtained by amplification of genomic DNA using the polymerase chain reaction. The 3 beta-HSD gene contains a 5'-untranslated exon of 53 base pairs (bp) and three successive translated exons of 232, 165, and 1218 bp, respectively, separated by introns of 129, 3883, and 2162 bp. The transcription start site is situated 267 nucleotides upstream from the ATG initiating codon. DNA sequence analysis of the 5'-flanking region reveals the existence of a putative TATA box (ATAAA) situated 28 nucleotides upstream from the transcription start site while a putative CAAT binding sequence is located 57 nucleotides upstream from the TATA box. Expression of a cDNA insert containing the coding region of 3 beta-HSD in nonsteroidogenic cells shows that the gene encodes a single 42-kDa protein containing both 3 beta-hydroxysteroid dehydrogenase and delta 5-delta 4-isomerase activities. Moreover, all natural steroid substrates tested are transformed with comparable efficiency by the enzyme. In addition to its importance for studies of the regulation of expression of 3 beta-HSD in gonadal as well as peripheral tissues, knowledge of the structure of the human 3 beta-HSD gene should permit investigation of the molecular defects responsible for 3 beta-HSD deficiency, the second most common cause of adrenal hyperplasia in children.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

Effects of human chorionic gonadotropin (hCG) and prolactin (PRL) on 3 beta-hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) expression and activity in the rat ovary.

Using a recently cloned rat ovary 3 beta-HSD cDNA and antibodies raised against purified human placental 3 beta-HSD, we have studied the effects of treatment with human chorionic gonadotropin (hCG) and hyperprolactinemia achieved by pituitary implants, alone or in combination, on the expression and activity of ovarian 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) in intact adult rats. 32P- and 35S-labeled cDNA probes were used to evaluate the effects of treatments on 3 beta-HSD mRNA levels by dot blot and in situ hybridization, respectively, while enzymatic activity was measured by the conversion of [14C]dehydroepiandrosterone into [14C]androstenedione. The present data show that hCG exerts a marked trophic effect on rat corpora lutea with an increase in total ovarian 3 beta-HSD mRNA levels, 3 beta-HSD protein content as well as enzymatic activity, resulting in an increase in serum progesterone levels. Prolactin-secreting pituitary implants alone, on the other hand, while exerting small effects on 3 beta-HSD expression and activity, led to a marked potentiation of the stimulatory effect of hCG on all parameters. The present data show that hCG and PRL act synergistically to stimulate ovarian progesterone secretion via an increase in 3 beta-HSD mRNA levels, protein content and enzymatic activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

Inhibitory effect of synthetic progestins, 4-MA and cyanoketone on human placental 3 beta-hydroxysteroid dehydrogenase/5----4-ene-isomerase activity.

Human placental 3 beta-hydroxysteroid dehydrogenase/5----4-ene isomerase (3 beta-HSD) purified from human placenta transforms C-21 (pregnenolone and 17 alpha-hydroxy pregnenolone) as well as C-19 (dehydroepiandrosterone and androst-5-ene-3 beta, 17 beta-diol) steroids into the corresponding 3-keto-4-ene-steroids and is thus involved in the biosynthesis of all classes of hormonal steroids. Trilostane, epostane and cyanoketone are potent inhibitors of 3 beta-HSD with Ki values of approximately 50 nM. 4-MA, a well known 5 alpha-reductase inhibitor, is also a potent inhibitor of 3 beta-HSD with a Ki value of 56 nM. Synthetic progestin compounds such as promegestone and RU2323 show relatively strong inhibitory effects with Ki values of 110 and 190 nM, respectively. Cyproterone acetate, a progestin used in the treatment of hirsutism, acne and prostate cancer as well as norgestrel and norethindrone that are widely used as oral contraceptives also inhibit 3 beta-HSD activity at Ki values of 1.5, 1.7 and 2.5 microM, respectively.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

Light microscopic immunocytochemical localization of 3 beta-hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4-isomerase in the gonads and adrenal glands of the guinea pig.

The enzyme complex 3 beta-hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4-isomerase (3 beta HSD) is involved in the biosynthesis of all classes of active steroids, namely glucocorticoids, mineralocorticoids, progesterone, and sex hormone steroids. To obtain precise information about the cellular and subcellular localization of 3 beta HSD in the gonads and adrenals of the guinea pig, we have proceeded to immunocytochemical localization of the enzyme using antibodies developed against purified human placental 3 beta HSD. In the testis, specific immunostaining was restricted to the cytoplasm of the interstitial cells. In the ovary, on the other hand, immunostaining was found in the cytoplasm of the cells of the corpus luteum and theca interna. The granulosa cells of the follicles were not immunolabeled, with the exception of one layer of cells in contact with the zona pellucida. This restricted labeling was observed in growing and mature follicles, but not in primordial and small primary follicles. In the adrenals, the three zones of the cortex were labeled, whereas no staining could be detected in the medulla. Contrary to findings in the testis and ovary, staining was found in both the cytoplasm and nuclei of adrenocortical cells. The present data suggest a functional interaction between the ovocyte and the specialized layer of 3 beta HSD-containing granulosa cells which might play a role in ovocyte maturation.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

Localization of 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase in rat gonads and adrenal glands by immunocytochemistry and in situ hybridization.

The enzyme complex delta 5-3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta HSD) is involved in the biosynthesis of all classes of steroids, namely glucocorticoids, mineralocorticoids, progesterone, and sex steroids. To obtain information on the precise localization of 3 beta HSD in rat gonads and adrenal glands, two complementary cytochemical techniques were used; immunocytochemical localization was achieved with antibodies developed against purified human placental 3 beta HSD, while 3 beta HSD mRNA localization was achieved by in situ hybridization performed with a recently cloned rat 3 beta HSD cDNA. In the testis, specific immunostaining was restricted to the cytoplasm of the interstitial cells, while by in situ hybridization, specific silver grains were also seen over the interstitial cells. In the ovary, immunostaining was found in the cytoplasm of cells of the corpus luteum and theca interna, while the granulosa cells of the follicles showed no positive reaction. By in situ hybridization, a specific hybridization signal was observed over granulosa cells of the corpus luteum, which are mainly responsible for progesterone secretion, and to a lesser extent over theca interna cells, known for their role in secreting C19 androgens. In the adrenals, the three zones of the cortex were equally immunolabeled, whereas no staining could be detected in the medulla. Similarly, by in situ hybridization, silver grains were located over the zona glomerulosa, fasciculata, and reticularis, while no specific autoradiographic reaction could be observed on the chromaffin cells of the medulla. The present study provides new information about the precise cellular localization of 3 beta HSD in the adrenal glands and gonads in the rat, thus providing useful information about the site of action of 3 beta HSD, especially in the gonads. Moreover, the approaches used for localization studies, especially quantitative in situ hybridization, should provide a useful tool for assessing the role of hormones on 3 beta HSD expression in the different compartments of the gonads and adrenal glands.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

Changes in 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase messenger ribonucleic acid, activity and protein levels during the estrous cycle in the bovine ovary.

A 1169 base pair fragment of bovine 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) cDNA was used to quantitate 3 beta-HSD messenger RNA (mRNA) levels in the bovine ovary during the estrous cycle. The content of 3 beta-HSD protein was measured by immunoblot analysis using an antiserum developed in rabbits against human 3 beta-HSD, whereas 3 beta-HSD activity was measured using [3H]pregnenolone, [3H] dehydroepiandrosterone, and [3H]androst-5-ene-3 beta,17 beta-diol as substrates. There was a parallel increase in 3 beta-HSD mRNA, protein content, and enzymatic activity levels from days 1-3 after estrus to maximal values at 50-100% above control on days 8-11 after estrus. Thereafter, all values decreased progressively until days 16-17 before a dramatic fall to 5% or less than maximal values on days 18-20 after estrus. Almost superimposable results of enzymatic activity were obtained with the three substrates, thus suggesting a unique 3 beta-HSD or parallel changes in the activity of multiple 3 beta-HSDs. The above-described changes observed during the luteal phase are almost exclusively due to variations in corpora lutea. In fact, 3 beta-HSD activity in ovarian follicles was approximately 10,000 lower than that measured in corpora lutea. The close correlation observed over a wide range of 3 beta-HSD mRNA, protein content, and activity levels suggests that changes of ovarian 3 beta-HSD activity are controlled at the level of 3 beta-HSD gene expression and/or 3 beta-HSD mRNA stability.

Animals↗
PubMed1990

Regulation of 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase expression and activity in the hypophysectomized rat ovary: interactions between the stimulatory effect of human chorionic gonadotropin and the luteolytic effect of prolactin.

The enzyme 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) catalyzes an obligatory step in the conversion of pregnenolone and other 5-ene-3 beta-hydroxysteroids into progesterone as well as precursors of all androgens and estrogens in the ovary. Since 3 beta-HSD is likely to be an important target for regulation by pituitary hormones, we have studied the effect of chronic treatment with LH (hCG), FSH, and PRL on ovarian 3 beta-HSD expression and activity in hypophysectomized adult female rats. Human CG (hCG) [10 IU, twice a day (bid)], ovine FSH (0.5 microgram, bid), and ovine PRL (1 mg, bid) were administered, singly or in combination, for a period of 10 days starting 15 days after hypophysectomy. In hypophysectomized rats, PRL exerted a potent inhibitory effect on all the parameters studied. In fact, PRL caused a 81% decrease in ovarian 3 beta-HSD mRNA content accompanied by a similar decrease in 3 beta-HSD activity and protein levels. In addition, ovarian weight decreased by 40% whereas serum progesterone fell dramatically from 1.92 nmol/liter to undetectable levels after treatment with PRL. Whereas hCG alone had only slight stimulatory effects on 3 beta-HSD mRNA, protein content and activity levels, treatment with the gonadotropin partially or completely reversed the potent inhibitory effects of oPRL on all the parameters measured. FSH, on the other hand, had no significant effect on 3 beta-HSD expression and activity. In situ hybridization experiments using the 35S-labeled rat ovary 3 beta-HSD cDNA probe show that the inhibitory effect of PRL is exerted primarily on luteal cell 3 beta-HSD expression and activity. On the other hand, it can be seen that hCG stimulates 3 beta-HSD mRNA accumulation in interstitial cells. The present data show that hCG and PRL exert potent and opposite cell-specific effects on ovarian 3 beta-HSD expression, activity, and content in the rat ovary. Moreover, the present study could suggest that female infertility associated with hyperprolactinemia in women could well be related, at least in part, to the potent inhibitory effect of PRL on ovarian 3 beta-HSD expression and activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

Structure of two in tandem human 17 beta-hydroxysteroid dehydrogenase genes.

Two human 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) genes (h17 beta-HSDI and h17 beta-HSDII) included in tandem within an approximately 13 kilobase pair fragment were isolated from a genomic lambda EMBL3 DNA library using cDNA encoding human 17 beta-HSD (hpE2DH216) as probe. We have determined the complete exon and intron sequences of the two genes as well as their 5' and 3'-flanking regions. Human 17 beta-HSDII contains six exons and five short introns for a total length of 3250 base pairs. The exon sequence of h17 beta-HSDII is identical to the previously reported hpE2DH216 cDNA while the overlapping nucleotide sequences of the corresponding exons and introns of h17 beta-HSDI and h17 beta-HSDII show 89% homology. In addition, we have used the hpE2DH216 cDNA to demonstrate the widespread expression of 17 beta-HSD mRNAs in steroidogenic and peripheral target tissues. These new findings provide the basis for a better understanding of the molecular mechanisms involved in 17 beta-HSD deficiency and peripheral sex steroid metabolism.

17-Hydroxysteroid Dehydrogenases↗