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Query: UNIPROT:P56851 (epididymal)
 11,273 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of the antiandrogenic effect of 5,10-seco-19-norpregnane-4,5-diene-3,10,20-trione (secosteroid), reputedly an irreversible inhibitor of 5 alpha-reductase, was investigated. Its addition (10 microM) to culture media effectively suppressed the synthesis of rat epididymal proteins specifically induced by 0.1 microM testosterone (T) or dihydrotestosterone (DHT). Under the same conditions, secosteroid did not change the rate at which labeled T was metabolized to 5 alpha-reduced compounds. In a comparative study, secosteroid inhibited 5 alpha-reductase in an isolated microsomal fraction while not affecting the enzyme activity in minced tissue. Secosteroid was shown to be a competitor of the binding of [3H]T and [3H]DHT (both at 4 nM) to the epididymal cytosol androgen receptor, with ID50 of 1 microM for the former and 4 microM for the latter, thus explaining the mechanism involved in its antiandrogenic properties.
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PMID:Studies on the mechanism of the antiandrogenic effect of a putative 5 alpha-reductase inhibitor. 362 56

We measured the 5 alpha-reductase activity in isolated cell preparations of rat adipose tissue using the formation of [3H]dihydrotestosterone from [3H]testosterone as an endpoint. Stromal cells were prepared from the epididymal fat pad, perinephric fat, and subcutaneous fat of male rats and from perinephric fat of female rats. Adipocytes were prepared from the epididymal fat pad and perinephric fat of male rats. Stromal cells from the epididymal fat pad and perinephric fat contained greater 5 alpha-reductase activity than did the adipocytes from these depots. Stromal cells from the epididymal fat pad contained greater activity than those from perinephric and subcutaneous depots. Perinephric stromal cells from female rats were slightly more active than those from male rats. Estradiol (10(-8) M), when added to the medium, caused a 90% decrease in 5 alpha-reductase activity. Aromatase activity was minimal, several orders of magnitude less than 5 alpha-reductase activity in each tissue studied.
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PMID:5 alpha-reductase activity in rat adipose tissue. 367 52

The epididymal epithelial ultrastructure has been described in the adult male North American opossum, Didelphis virginiana. Morphological results have suggested that absorptive activity is prominent in the proximal epididymal region by virtue of numerous microvilli, an endocytotic complex, dense granules, and multivesicular bodies in the apical cytoplasm. In contrast, the middle and distal epididymal regions exhibit ultrastructural features indicative of protein synthesis such as large invaginated euchromatic nuclei, large nucleoli, and increased amounts of granular endoplasmic reticulum. It is in the middle and distal epididymal regions where sperm head rotation and sperm pairing take place. Epididymal delta 4-3-ketosteroid-5 alpha-oxidoreductase (5 alpha-reductase) activity also has been measured. It has been found that the level of enzyme activity differs significantly (p less than 0.01) between the proximal, middle, and distal epididymal regions. Enzyme-specific activity has been found to be highest in the middle region (47.6 +/- 5.4 picomoles 5 alpha-reduced androgens formed/b/mg protein), lower in the distal region (18.3 +/- 0.7 picomoles 5 alpha-reduced androgens formed/b/mg protein), with little activity (2.4 +/- 1.2 picomoles 5 alpha-reduced androgens formed/h/mg protein) found in the proximal epididymal region. This regional distribution of enzyme activity differs markedly from that reported for eutherian mammals. Both the suggested epididymal protein synthetic and secretory activity and the level of epididymal 5 alpha-reductase activity appear to correlate regionally with the morphological changes that occur in the opossum spermatozoa as they transit the epididymis.
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PMID:Unique regional distribution of delta 4-3-ketosteroid-5 alpha-oxidoreductase and associated epididymal morphology in the marsupial, Didelphis virginiana. 367 95

Androgen metabolism in human epididymis was studied by incubating tissue fragments with isotopically labeled testosterone (T) and androstenedione (A) under batch and superfusion conditions. Epididymides were obtained from 16 patients with prostatic cancer, 5 of them treated with diethylstilbestrol (2.5 mg/d) for several months prior to castration. Results from batch incubations with [3H]T (100 nM) for 2 h at 25 degrees C indicated a markedly lower 5 alpha-reductase activity in tissues from estrogen-treated patients, as evaluated by measuring the amounts of radioactive 5 alpha-dihydrotestosterone, 5 alpha-androstanediols and 5 alpha-androstanedione present in tissue and medium at the end of the incubation period. Superfusion experiments confirmed this estrogen effect and also showed a shift of the interconversion between A and T towards the reductive direction and a diminished tissue retention of DHT after estrogen treatment. These effects may contribute to the marked regression of the epididymal epithelium that was noted in the estrogen-treated patients, which is thought to be mainly the result of the inhibition of androgen biosynthesis caused by chemical hypophysectomy.
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PMID:Androgen metabolism in the human epididymis. Effect of in vivo estrogen administration. 374 23

Epididymal 5 alpha-reductase converts testosterone to 5 alpha-dihydrotestosterone. The enzyme is localized to the nuclear and microsomal membranes, and using two approaches, we investigated the relationship between 5 alpha-reductase activity and the membrane environment. In the first, nuclear and microsomal membrane fractions were treated with phospholipases to modify specifically the structure of the phospholipid component of the membranes, and the effects of these treatments on the kinetic parameters of 5 alpha-reductase were examined. The second approach was to observe the effects of phospholipids of known structure on solubilized 5 alpha-reductase activity. Treatment of the membrane fractions with phospholipase C increased the Km(app) of both the nuclear and microsomal 5 alpha-reductases for testosterone. Phospholipase A2 treatment also increased the Km(app) of the microsomal enzyme, but in contrast, the Km(app) of the nuclear 5 alpha-reductase for testosterone was unaffected. This demonstrated a fundamental difference in the role of the membrane environment in the expression of 5 alpha-reductase activity in these subcellular compartments. The ability of phospholipids to enhance the activity of solubilized 5 alpha-reductase was highly specific and structure related. Only phosphatidylcholines containing either unsaturated acyl chains or saturated acyl chains of 12 carbon atoms were found to activate 5 alpha-reductase. The most potent activator was dilauroyl phosphatidylcholine, which reduced the Km(app) values of both nuclear and microsomal 5 alpha-reductases for testosterone, without affecting the concentration of active 5 alpha-reductase (Vmax(app) ). This is the first time that an activator of 5 alpha-reductase has been found. These findings suggest that epididymal 5 alpha-reductase activity may be regulated by changes in the phospholipid environment.
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PMID:Modulation of epididymal delta 4-steroid 5 alpha-reductase activity in vitro by the phospholipid environment. 399 84

Histochemical studies of the rat epididymis after treatment with alp ha-chlorohydrin (U-5897) are presented. 14 sexually mature male rats received either daily subcutaneous injections of 50 mg U-5907/kg body weight or distilled water for 20 days. The animals were sacrificed the day following the last injection. U-5897 induced temporary sterility as demonstrated by blocked transport of spermatozoa, and spermatogenic cells eliminated from the spermatogenic epithelium which became blocked in the caudal part of the epididymis. This resulted in the distension of the segment of the distal part of the epididymal duct and to the thinning of the epithelium which lined the altered segment. Alkaline and acid phosphatases, nonspecific esterases, succinate and glucose-6-phosphate dehydrogenases and reduced nicotinamide-adenine dinucleotide tetrazolium reductase in the unchanged part of the epididymal duct were comparable to control rats whereas the altered part of the epididymis showed these activities to much weaker degrees or to be absent altogether.
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PMID:Histochemical studies of the rat epididymis after treatment with alpha-chlorohydrin (U-5897). 415 41

The 5 alpha-reductase activity was assayed in homogenates of stroma and epithelium in the rat ventral prostate and epididymis. Samples consisting of a 0.3 mg/ml tissue protein in TES buffer, pH 7.0 were incubated at 37 degrees C for 30 min in the presence of 50 nM [1,2-3H]testosterone and a NADPH-generating system started with 5 x 10(-4) M NADP. The yield of 5 alpha-reduced metabolites, as established by using thin-layer chromatography, gave an estimate of enzyme activity. Whereas the specific activity of 5 alpha-reductase was highest in prostatic stroma and epididymal epithelium, most of the total enzyme activity was associated with the epithelium in both the prostate and epididymis. The effect of dihydrotestosterone on specific activity of 5 alpha-reductase was studied by administering the hormone to 7-day castrated rats. In prostate, the specific activity of both stromal and epithelium forms of the enzyme reached a maximum after 4 days of treatment. In epididymis only the epithelial form of 5 alpha-reductase underwent a major change in specific activity, the latter peaking after 8-12 days of treatment. Furthermore, while the total activity of 5 alpha-reductase in the prostatic tissue fractions could be induced by as much as 4-fold the normal control values, the epididymal enzyme could not be induced above the normal level either in the stroma or the epithelium. This may explain the relative resistance of epididymis to abnormal growth stimulation under the influence of hormones.
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PMID:5 alpha-reductase activity in stroma and epithelium of rat prostate and epididymis. A contribution to elucidation of the mechanism for development of hyperplastic growth of prostatic tissue. 619 Mar 38

We report here the structural assignment for the hydroxylated 5 alpha-reduced metabolites in the culture medium following incubation of radiolabelled testosterone with explants of rat ventral prostate, canine cauda epididymidis and prostate, and benign hyperplastic canine and human prostate. Explants were incubated for 21 h at 37 degrees C in surface contact with serum-free Trowell's T8 medium containing 1.7 microM or 8.5 nM substrate. After uptake determination, radiosteroid patterns in explants and media were obtained by t.l.c. The C19O3-metabolites released into the culture medium were resolved by h.p.l.c. and fractions migrating with appropriate reference compounds were crystallized to constant SA with carriers synthesized for this purpose. 5 alpha-Androstane-3 beta,6 alpha,17 beta-triol and 3 beta,6 alpha-dihydroxy-5 alpha-androstan-17-one were identified as the major C19O3-radiometabolites of rat ventral prostate. In the culture medium of canine prostate and epididymis and human prostate, 5 alpha-androstane-3 beta,7 alpha,17 beta-triol and 3 beta,7 alpha-dihydroxy 5 alpha-androstan-17-one were the principal hydroxylation products, with 6 alpha-hydroxy epimers as significant minor products of the canine prostate and epididymis and 5 alpha-androstane-3 beta,7 beta,17 beta-triol as a significant minor radiometabolite of human prostate tissue. Treatment of the castrated dog with androgen and estrogen causes an oxidative shift to striking predominance of 3 beta,7 alpha-dihydroxy 5 alpha-androstan-17-one. The 3 beta-hydroxy-5 alpha-androstane configuration of the identified C19O3-metabolites supports a pathway of prostatic and epididymal testosterone disposition which effects activation by 5 alpha-reductase and inactivation and egress by the coupled 5 alpha-3-oxosteroid reductase/3 beta-hydroxysteroid hydroxylase reactions.
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PMID:Metabolism of radiotestosterone to 3 beta,6 alpha- and 3 beta,7 alpha-dihydroxy 5 alpha-steroids by rat ventral, canine and human prostate in organ culture. 633 21

The curve of the specific activity of rat epididymal nuclear delta 4-5 alpha-reductase is bell shaped as a function of age, whereas that of cytoplasmic 3 alpha-hydroxysteroid dehydrogenase does not change significantly with age. The present study examines the subcellular distribution of delta 4-5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase in the caput-corpus and cauda epididymidis during development. A 5-step discontinuous sucrose gradient was developed for fractionation of epididymal homogenates. By using enzyme markers specific for different subcellular organelles, the five different subcellular fractions obtained were shown to be of cytoplasmic, microsomal, mitochondrial, nuclear and spermatozoal origin. 3 alpha-Hydroxysteroid dehydrogenase activity was associated only with the cytoplasmic fraction. The activity of the enzyme did not change significantly with age in either the caput-corpus or cauda epididymidis. delta 4-5 alpha-Reductase activity was found in fractions containing microsomal and nuclear markers. delta 4-5 alpha-Reductase activity in the nuclear fraction of the caput-corpus epididymidis was evident in the youngest age group (Day 25), increased 4-fold and peaked in the next age group (Day 35), and declined with each successive age group: Day 45 (60% of maximum), Day 60 (20% of maximum), Day 75 (15% of maximum) and Day 105 (10% of maximum). In contrast, microsomal delta 4-5 alpha-reductase activity increased successively from Day 25 to Day 105; enzyme activity doubled between these two ages. The ratio of nuclear to microsomal delta 4-5 alpha-reductase activity from the caput-corpus epididymidis thus changed markedly with age: Day 25:1.32; Day 35:3.76; Day 45:2.44; Day 60:1.03; Day 75:0.41; and Day 105:0.21. In the cauda epididymidis nuclear delta 4-5 alpha-reductase activity was only evident at Day 35 and Day 45; in microsomal fractions, activity was first found at Day 35 and did not subsequently change with age. These results demonstrate that: 1) epididymal 3 alpha-hydroxysteroid dehydrogenase activity is found only in the cytoplasmic fraction; 2) delta 4-5 alpha-reductase activity is found in nuclear and microsomal fractions; and 3) the subcellular distribution of delta 4-5 alpha-reductase activity changes markedly with age and epididymal section, suggesting differential regulation of nuclear and microsomal delta 4-5 alpha-reductase activities.
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PMID:Subcellular distribution of steroid delta 4-5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase in the rat epididymis during sexual maturation. 657 16

The triazine dyes, Cibacron blue F3GA and Procion red HE3B inhibited diaphorase activity of ferredoxin-NADP+ reductase, in a competitive manner with respect to NADPH. The Ki values were 1.5 and 0.2 microM, respectively. Binding of the dyes to the flavoprotein, as measured by difference spectroscopy, indicated an apparent stoichiometry of 1 mol dye/mol reductase and was prevented by NADP+ or high ionic strength. Chemical modification of a lysine residue and a carboxyl group at the NADP(H) binding site of the enzyme prevented complex formation with Procion red. Procion red showed a higher affinity for ferredoxin-NADP+ reductase than Cibacron blue. The Kd values were 1.9 and 5 microM, respectively. Once covalently linked to a Sepharose matrix, the triazine compounds specifically bind the flavoprotein. The interaction is partially electrostatic and partially hydrophobic. The enzyme can be eluted by high concentrations of salt or low concentrations of the corresponding coenzyme. The use of this affinity column allows the rapid purification of ferredoxin-NADP+ oxidoreductase from spinach leaves with good yields.
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PMID:Interaction of ferredoxin-NADP+ oxidoreductase with triazine dyes. A rapid purification method by affinity chromatography. 682 90


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