Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Epididymal delta 4-steroid 5 alpha-reductase (cholestenone 5 alpha-reductase), the enzyme that catalyses the conversion of testosterone into the biologically active metabolite dihydrotestosterone (17 beta-hydroxy-5 alpha-androstan-3-one), is a membrane-bound enzyme found in both nuclear and microsomal subcellular fractions. In order to characterize epididymal delta 4-steroid 5 alpha-reductase, it was first necessary to solubilize the enzymic activity. Of the various treatments tested, a combination of 0.5% (w/v) Lubrol WX, 0.1 M-sodium citrate and 0.1 M-KCl maintained enzymic activity at control values and solubilized 66% of total epididymal delta 4-steroid 5 alpha-reductase activity in an active and stable form. The sedimentation coefficient of solubilized delta 4-steroid 5 alpha-reductase, as determined in continuous sucrose density gradients, was greater for the microsomal than for the nuclear enzyme (11.6S compared with 10.1S). Although the apparent Km values of the enzyme for testosterone were similar in nuclear and microsomal subcellular fractions (range 1.75 x 10(-7) - 4.52 x 10(-7)M), the apparent Km of the enzyme for NADPH was about 30-fold greater for the microsomal enzyme than for the nuclear enzyme. The apparent Km of the enzyme for either substrate was not significantly altered after solubilization. The relative capacity of steroids to inhibit the enzymic activity, the pH optima and the effects of Ca2+ and Mg2+ were similar for membrane-bound and solubilized delta 4-steroid 5 alpha-reductase in both the nuclear and the microsomal fractions. The results reported demonstrate that epididymal delta 4-steroid 5 alpha-reductase can be solubilized in an active and stable form with no significant changes in the kinetic characteristics of the enzyme after solubilization; furthermore, kinetic and molecular-size differences observed for the nuclear and the microsomal forms of the enzyme suggest that there may exist at least two forms of epididymal delta 4-steroid 5 alpha-reductase.
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PMID:Solubilization and partial characterization of rat epididymal delta 4-steroid 5 alpha-reductase (cholestenone 5 alpha-reductase). 687 Aug 29

delta 4-5 alpha-Reductase activity is apparently regulated by a testicular factor(s) secreted directly into the epididymis, whereas 3 alpha-hydroxysteroid dehydrogenase activity, in this tissue, appears to reflect circulating androgen levels. To test whether the factor(s) regulating delta 4-5 alpha-reductase activity is directly associated with spermatozoa, a developmental study was undertaken to temporally correlate various parameters of the male reproductive tract with enzymatic activities. delta 4-5 alpha-Reductase activity is first detectable at 21 days of age. Activity increases until day 77, after which time enzymatic activity decreases by more than 60%, reaching steady adult values at 105 days. 3 alpha-Hydroxysteroid dehydrogenase activity is detectable as early as 7 days. Levels of this enzyme increase until day 63, after which time constant adult values are maintained until at least 1 yr. Spermatids and/or spermatozoa are first seen in the testes at 42 days, and plateau levels are reached by day 77. Spermatozoa are first seen in the epididymis at 49 days and reach maximal values by 91 days; no significant change occurs thereafter (until 365 days). Increases in seminal vesicle and ventral prostate weights are of a sigmoidal type, paralleling increases in plasma androgens, with the greatest rate of rise between days 35--63. This sigmoidal type of increase in tissue weights and plasma androgens is similar to that seen for epididymal 3 alpha-hydroxysteroid dehydrogenase but markedly different from that found for delta 4-5 alpha-reductase. The importance of delta 4-5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase activities in the epididymis before the entry of spermatozoa and the decline in delta 4-5 alpha-reductase activity with age is discussed.
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PMID:Steroid delta 4-5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase in the rat epididymis during development. 693 15

The effect of age on in vivo tritiated testosterone (3H-T) metabolism and on epididymal 5 alpha-reductase and 3 alpha/beta-hydroxysteroid dehydrogenase activity has been studied on male Wistar rats. Following i.m. injection of 3H-T to 3 and 25 month old functionally hepatectomized rats, the accumulation of 5 alpha-androstan-17 beta-ol-3-one (DHT) by both the caput and cauda epididymidis, prostate, and seminal vesicles was significantly higher in the younger animals than in the old. The total conversion of 3H-T by both epididymal segments was unaltered with advancing age whereas a significant decrease was observed in both prostate and seminal vesicles. The ratio between 17 beta-hydroxy and 17-keto metabolites in the prostate and epididymis of both hepatectomized and intact animals decreased significantly with age. The ratio values for the seminal vesicles showed no significant age variation. The formation of total 5 alpha-reduced metabolites by epididymal homogenates showed a linear decrease with advancing age. The activity of 5 alpha-reductase fell from 16.1 to 10.3 ng/mg protein/30 min. 3 alpha/beta-hydroxysteroid dehydrogenase activity was unaffected by age. The reduced levels of active testosterone metabolites reported with old age are a result of a decrease in 5 alpha-reductase activity, the ultimate cause of which is most probably an age associated defect in the hypothalamic-pituitary-testicular feedback system.
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PMID:Androgen metabolism by rat epididymis. 8 Age dependent changes in androgen metabolizing enzymes in rat accessory sex organs. 694 45

When [4-14C]-5 alpha-dihydrotestosterone was incubated with the homogenate of human epididymis, 5 alpha-androstane-3 alpha, 17 beta-diol and 5 alpha-androstane-3 beta, 17 beta-diol were identified as major metabolites. The ratio of 3 alpha- to 3 beta-epimer in androstanediol formation was approximately 2.4. 5 alpha-Androstane-3, 17-dione was also identified as a minor metabolite. Among the subcellular fractions, both the human epididymal 3 alpha- and 3 beta-hydroxysteroid dehydrogenases were localized almost exclusively in the cytosol fraction (105,000 X g supernatant). Both enzymes had optimum pH at 7.5 and optimum temperature at 46 degrees C. NADPH was a more preferable cofactor than NADH for both dehydrogenases. The Michaelis constants (Km) of 3 alpha- and 3 beta-hydroxysteroid dehydrogenase for 5 alpha-dihydrotestosterone were similar and estimated as 8 X 10(-5) M, but the enzymes were unsaturable with the substrate under the conditions investigated, indicating low affinity and high capacity of both dehydrogenases for 5 alpha-dihydrotestosterone. The human epididymal 5 alpha-reductase revealed a regional difference in activity. The 5 alpha-reductase activity in the most proximal part of the head (ductuli efferentes) was one seventh to one tenth the activity in the remaining part of the epididymis which was constructed of ductus epididymis. Except for this finding, the activity of 5 alpha-reductase was highest in the head, then declined along the course to the tail portion. The 5 alpha-reductase for testosterone was competitively inhibited by delta 4-3-oxosteroids such as progesterone, 20 alpha-dihydroprogesterone, 17 alpha-hydroxyprogesterone, 4-androstenedione, 11-deoxycorticosterone, corticosterone and 11-deoxycortisol, which had inhibition constants (Ki) of 3.3 X 10(-9) M, 2.2 X 10(-9) M, 1.8 X 10(-8) M, 1.3 X 10(-8) M, 8.3 X 10(-9) M, 1.5 X 10(-7) M and 8.7 X 10(-8) M, respectively, suggesting the possibility that the 5 alpha-reduction of testosterone is regulated by other delta 4-3-oxosteroids.
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PMID:Studies on the human epididymis: partial characterization of 3 alpha- and 3 beta-hydroxysteroid dehydrogenase, regional distribution of 5 alpha-reductase and inhibitory effect of 4 delta-3-oxosteroids on 5 alpha-reductase. 696 21

The mammalian epididymis is the site where spermatozoa are matured and then stored. Though many studies have described epididymal functions and their regulation, little is known about how aging affects this tissue. The Brown Norway rat, which does not show the many age-related pathologies common to other rat strains, was used as a model to study aging of the epididymis. The present study was designed to determine the effect of aging on the mRNA levels for selected markers of epididymal function. Brown Norway rats ranging in age from 6 to 30 months were examined at 6-month intervals; epididymides were sectioned into caput-corpus and cauda regions. Relative mRNA concentrations were assessed using Northern blot analysis and specific cDNAs for the rat 5 alpha-reductase isozymes, types 1 and 2; proenkephalin; the androgen receptor; epididymal proteins B/C and D/E; and sulfated glycoprotein-2 (SGP-2, clusterin). Northern blots were quantitated by densitometric scanning. In the caput-corpus epididymidis, 5 alpha-reductase type 1 and type 2 mRNA levels decreased significantly by 43% and 33%, respectively, between 6 and 12 months and by 64% and 40%, respectively, between 6 and 30 months. No significant change, however, was found in the expression of the 5 alpha-reductase mRNAs in the cauda epididymidis. Interestingly, proenkephalin mRNA was only detected in the caput-corpus epididymidis of 6-month-old rats. In marked contrast to the 5 alpha-reductase isozymes and proenkephalin, no significant age-related changes were observed in the mRNA levels for the androgen receptor, protein B/C, or protein D/E. No age-related changes in mRNA expression for SGP-2 occurred in the caput-corpus epididymidis. However, in the cauda epididymidis, SGP-2 mRNA levels rose by twofold between 6 and 18 months and then decreased sharply by 75% between 18 and 30 months. We conclude that as the epididymis ages, the expression of genes for certain specific markers of epididymal function is affected in a region-specific manner. Further, the decrease in the concentrations of the mRNAs for the 5 alpha-reductase isozymes and proenkephalin in the epididymis between 6 and 12 months is thus far the earliest marker for aging in the male reproductive tract of the Brown Norway rat.
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PMID:Gene expression in the aging brown Norway rat epididymis. 755 40

It is well established that the epididymis is the site where spermatozoa are matured and stored, but our understanding of the regulation of epididymal epithelium functions and their effects on spermatozoa is still fairly limited. The most active regulator of epididymal functions seems to be dihydrotestosterone, the 5 alpha-reduced metabolite of testosterone. Our laboratory has focused on the regulation of 5 alpha-reductase, with studies encompassing its messenger RNA, protein and enzyme activity. We have also investigated the hormonal regulation and distribution of other specific key proteins found in epididymal epithelial cells that play critical roles in the function of these cells. These proteins include clusterin or sulfated glycoprotein-2 and the glutathione S-transferases (GST). Using complementary experimental approaches, including orchidectomy and hormonal replacement, efferent duct ligation, and developmental studies, we have established that 5 alpha-reductase enzyme activity is present in both nuclear and microsomal fractions; the nuclear enzyme appears almost exclusively in the initial segment of the epididymis. In addition, 5 alpha-reductase activity and the mRNAs for both the type 1 and type 2 form of the enzyme are regulated differentially with respect to age and site within the epididymis. Immunolocalization of the protein has revealed that it is located in principal cells and that its subcellular location is dependent on the region of the epididymis. These results indicate that there is both transcriptional and post-transcriptional regulation of the expression of 5 alpha-reductase. Clusterin is a hydrophobic protein secreted by Sertoli cells and found in high concentration in the epididymis. This glycoprotein is expressed at its highest levels in the initial segment and caput epididymidis and at very low levels in the corpus and cauda epididymidis of the intact rat, and it exhibits a novel pattern of androgen regulation. In the areas of highest expression, there is no androgen dependence; however, orchidectomy causes a dramatic increase in the message for clusterin, which is suppressible by androgens in the segments where expression is normally lowest. The GSTs are a family of enzymes thought to play a key role in detoxification. Members of the GST family are expressed in a region-dependent manner along the rat epididymis. We have found that the localization of one member of this enzyme family, GST P, or subunit Yp, is selective for basal cells in the corpus and cauda epididymidis.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Regulation of epididymal epithelial cell functions. 771 Nov 92

Adult male Sprague-Dawley rats were injected subcutaneously (s.c.) for 21 days either with the synthetic steroid 17 beta-methoxy-17-methyl-(5 alpha)-1 H'-androstane-(3,2-c) pyrazole (17MM) at two dose levels (0.1 and 1 mg/kg/day) or with the vehicle used to dilute the steroid. At autopsy, caput epididymes and ventral prostates were removed and incubated in vitro. The effect on the 5 alpha-reductase (5 alpha-R) activity was evaluated by measuring the amounts of DHT formed from 14C-testosterone (14C-T) used as the substrate. The in vivo administration of 17MM at the dose of 0.1 mg/kg/day resulted in a significant decrease in the formation of DHT at the level of the epididymis, while there was no effect on the prostate. The dose of 1 mg/kg/day did not induce any modification in the formation of DHT in either organ. The determination of serum LH showed that the treatment with either dose did not alter serum LH titers. These findings suggest that the in vivo treatment with 17MM lowers the in vitro formation of DHT from T at the epididymal, but not at the prostatic level and consequently suggests a selective inhibitory effect of 17MM on the 5 alpha-R present in the epididymis.
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PMID:Effect of the in vivo treatment with the synthetic steroid 17 beta-methoxy-17-methyl-(5 alpha)-1 H'-androstane-(3,2-c) pyrazole (17MM) on the in vitro formation of DHT in the epididymis of the rat. 794 8

Dihydrotestosterone (DHT), the active androgen in many tissues, is synthesized from testosterone by the enzyme 4-ene steroid 5 alpha-reductase (5 alpha-reductase; EC 1.3.1.22). In the epididymis, the maturation and storage of spermatozoa are dependent on the presence of 5 alpha-reduced androgens. The regulation of epididymal 5 alpha-reductase is complex. To date, the regulation of this enzyme has been studied extensively at the level of enzymatic activity and more recently at the mRNA level. Regulation at the level of the protein, however, remains poorly understood. We have raised rabbit polyclonal antibodies to a 24-mer synthetic peptide whose sequence was determined from the predicted amino acid sequence for rat 5 alpha-reductase type 1 to immunolocalize the 5 alpha-reductase type 1 protein in the rat epididymis during postnatal development. Western blot analysis revealed a specific immunoreactive band of 26 kilodaltons in male rat liver, epididymis, and prostate; this apparent molecular size is identical to that obtained when the 5 alpha-reductase type 1 cDNA is expressed in mammalian cells. Furthermore, the relative protein levels, liver > epididymis > prostate, were consistent with the mRNA levels for type 1 rat 5 alpha-reductase. Perfusion-fixed paraffin-embedded epididymal tissue sections were used to immunolocalize type 1 5 alpha-reductase. In the adult rat epididymis, the most intense immunoperoxidase reaction was observed in a discrete lobule of the initial segment of the epididymis. A progressive decrease in staining intensity occurred distally along the tissue to the cauda epididymis. The staining reaction was specific to cytoplasmic elements of epithelial principal cells; no reaction was evident over nuclei. However, specifically in the initial segment, very intense staining was seen in the infranuclear region of the principal cells. In the proximal caput epididymidis, the staining was primarily confined to an oval region above the nuclei, whereas in the remaining epididymal regions, weak staining was seen throughout the cytoplasm. Thus, the intracellular localization of the 5 alpha-reductase type 1 protein changed as one moved down the epididymis. Finally, the pattern of immunolocalization of 5 alpha-reductase type 1 protein was different in the epididymis of rats of different postnatal ages. On day 7, no reactivity was noted; by day 28, a weak apical staining of principal cells was seen throughout the epididymis; by day 47, the adult pattern of staining had been established. Our results revealed that the expression and intracellular localization of the 5 alpha-reductase type 1 protein are both age dependent and epididymal segment specific.
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PMID:Immunocytochemical localization of 4-ene steroid 5 alpha-reductase type 1 along the rat epididymis during postnatal development. 815 33

Recent studies with vinclozolin, a dicarboximide fungicide, demonstrate that perinatal exposure to 100 mg vinclozolin/kg/day from Gestational Day 14 through Postnatal Day 3 inhibits morphological sex differentiation. At 1 year, treated male rats exhibited hypospadias, cleft phallus, suprainguinal ectopic testes, a vaginal pouch, epididymal and testicular granulomas, and atrophic seminal vesicles and ventral prostate glands. This pattern of malformations suggests that this fungicide possesses antiandrogenic activity. To test this hypothesis, we examined the ability of vinclozolin to inhibit the conversion of testosterone to the more potent androgen 5 alpha-dihydrotestosterone via 5 alpha-reductase (EC 1.3.1.22) and to compete with androgen for binding to the androgen receptor. The results indicate that neither vinclozolin nor its degradation products, 2-[[(3,5-dichlorophenyl)-carbamoyl]oxy]-2-methyl-3-butenoic acid (M1) and 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide (M2), inhibit 5 alpha-reductase activity. Although the ability of vinclozolin to compete with androgen for binding to the androgen receptor was weak (Ki > 700 microM), the two vinclozolin metabolites, M1 and M2, were effective antagonists of androgen receptor binding (Ki = 92 and 9.7 microM, respectively). As the concentrations of M1 in the serum of pregnant rats and their pups on Postnatal Day 3 meet or exceed the in vitro Ki for androgen receptor inhibition, we suggest that the demasculinizing effects of vinclozolin exposure in vivo also may be mediated via the antiandrogenic metabolites M1 and/or M2.
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PMID:Environmental hormone disruptors: evidence that vinclozolin developmental toxicity is mediated by antiandrogenic metabolites. 820 80

We have investigated phospholipid requirement for testosterone 5 alpha-reductase solubilized from microsomal and nuclear fractions of rat epididymis. The 5 alpha-reductase from microsomal fraction was stimulated by phosphatidylcholine (PC) with long acyl-chain lengths, but inhibited by short chain PC. The nuclear enzyme activity was weakly activated by PC with various acyl-chain lengths tested. Synthetic phosphatidylserine (PS), such as dioleoylPS, most strongly stimulated the microsomal enzyme activity, but did not exhibit any activation of the nuclear enzyme activity. Endogenous phospholipids, such as PC, PS, and phosphatidylethanolamine (PE) separated from bovine epididymal microsomes were tested for their stimulatory effects on microsomal and nuclear enzymes. Among these endogenous phospholipids, PS most greatly stimulated the microsomal 5 alpha-reductase activity, whereas both PC and PE weakly activated the enzyme activity. On the other hand, endogenous PC and PS had no ability to support the nuclear enzyme activity. The fatty acid compositions of PC and PS from bovine epididymal microsomes were determined, in order to elucidate the relationship between 5 alpha-reductase activation by these phospholipids and the structure of their acyl chains. The relative content of fatty acids in PC, in a decreasing order, was palmitate > linoleate > oleate; that in PS was stearate > oleate > palmitate. Based on these observations, the roles of microsomal PS and PC in epididymal 5 alpha-reductase reaction will be discussed.
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PMID:Phospholipid requirement of epididymal testosterone 5 alpha-reductase and phospholipid composition of epididymal microsomes. 825 57


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