Sex-Dependent Changes in Pituitary 5α:-Dihydrotestosterone and 3α-Androstanediol Formation During Postnatal Development and Puberty in the Rat

Denef, Carl; Magnus, Carew; McEwen, Bruce S.

doi:10.1210/endo-94-5-1265

Cited by 89 publications

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“…DHT formation in the latter group was not significantly higher than in adult male rats. These results per fectly agree with those previously obtained with intact pituitary glands [6],…”

Section: Total Pituitary Cell Populationsupporting

confidence: 93%

“…The cell pellet was washed with 2 ml ethanol, centrifuged and the supernatant removed. The com bined supernatants were dried under nitrogen and the testosterone and metabolites in the extract chrom atographed, quantitated and identified as described previously [6]. The principal metabolites were 5<x-DHT, 3a-androstanediol(53c-androstane-3a, 17/S-diol) and androst-4-ene-3,17-dione.…”

Section: Testosterone Metabolismmentioning

confidence: 99%

“…6, 9], Only limited information is available con cerning the mechanisms regulating the rate of pituitary DHT formation. It has been shown that androgens [5,6,11,14] and LHRH [10] significantly modulate DHT conversion rates. However, no data are available to rule out whether such changes are the consequence of alterations in the specific activity of the 5a-reductase per cell or of fluctuations in the proportional number of the cells that contain this enzyme.…”

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confidence: 99%

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Evidence that Pituitary 5<i>α</i>-Dihydrotestosterone Formation is Regulated through Changes in the Proportional Number and Size of the Gonadotrophic Cells

Denef

1979

Neuroendocrinology

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³H-testosterone was incubated and its conversion to 5α-reduced metabolites measured in dispersed anterior pituitary cells before and after separation into fractions with different cell-type distribution by gradient sedimentation at unit gravity. In pituitary cells from 14-day-old female rats, 5α-dihydrotestosterone (DHT) formation (expressed per 10⁵ cells) was several times higher than in those from 14-day-old male and adult male rats. After unit gravity sedimentation the formation of DHT rose with the proportional number and size of gonadotrophs in the fractions of all animal groups studied. In a highly purified population of large gonadotrophs, prepared from 14-day-old females, DHT formation was 23 times higher than in a highly purified population of large somatotrophs, obtained from adult males. Isopicnic sedimentation in a metrizamide gradient partially separated the highly purified preparation of gonadotrophs from contaminating thyrotrophs. In the latter gradient DHT formation was low in the fraction enriched in thyrotrophs. When homologous gradient fractions from the three animal groups studied were compared, differences in DHT formation were of similar rank order of magnitude as differences in the proportional number of gonadotrophs in these fractions. The fractional distribution pattern was highly characteristic for each animal group. It is concluded that pituitary DHT formation occurs primarily in the gonadotrophs and that changes in overall 5α-reductase activity of the pituitary is based, at least in part, on changes in the distribution profile of number and size of the gonadotrophs.

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“…DHT formation in the latter group was not significantly higher than in adult male rats. These results per fectly agree with those previously obtained with intact pituitary glands [6],…”

Section: Total Pituitary Cell Populationsupporting

confidence: 93%

Section: Testosterone Metabolismmentioning

confidence: 99%

mentioning

confidence: 99%

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Evidence that Pituitary 5<i>α</i>-Dihydrotestosterone Formation is Regulated through Changes in the Proportional Number and Size of the Gonadotrophic Cells

Denef

1979

Neuroendocrinology

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“…This result confirms previous reports describing similar tissue-specific and sexdependent differences of 5a-reductase activities (16,17,(35)(36)(37)(38). Two possible mechanisms that could determine this variability are allosteric modulation of enzyme activity or Proc.…”

Section: Discussionsupporting

confidence: 92%

Biosynthesis of catalytically active rat testosterone 5 alpha-reductase in microinjected Xenopus oocytes: evidence for tissue-specific differences in translatable mRNA.

Farkash

Soreq²,

Orly³

1988

Proc. Natl. Acad. Sci. U.S.A.

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The enzyme 4-ene-3-ketosteroid-5a-oxidoreductase [5a-reductase; 3-oxo-5a-steroid A4-dehydrogenase, 3-oxo-5a-steroid: (acceptor) EC 1.3.99.5] plays a key role in androgen-dependent target tissues, where it catalyzes the conversion of testosterone to the biologically active dihydrotestosterone. The regulation of 5a-reductase expression has not been studied at the molecular level as the enzyme is a membrane protein that is labile in cell-free homogenates. We developed a sensitive bioassay of the enzyme activity expressed in Xenopus oocytes microinjected with rat liver and prostate mRNA. After microinjection, incubation of intact oocytes in the presence of [3H]testosterone revealed the in ovo appearance of active 5a-reductase. Polyadenylylated RNA was fractionated by sucrose gradient centrifugation, and the enzymatic activity was shown to be encoded by a 1600-to 2000-base-pair fraction of hepatic poly(A) + RNA. 5a-Reductase mRNA was most efficiently translated when up to 80 ng of RNA was injected per oocyte. In the injected oocytes, 5a-reductase mRNA was found to be a short-lived molecule (til2 = 2 hr), whereas its in ovo translatable 5a-reductase protein exhibited stable enzymatic activity for over 40 hr. Moreover, the levels oftranslatable tissue-specific 5a-reductase mRNAs as monitored in the Xenopus oocytes correlated with the variable 5a-reductase activities in female rat liver, male rat liver, and prostate homogenates; the ratio of their specific activities was of 2500:630:1, respectively. Altogether, these results provide supporting evidence in favor of the transcriptional control of 5a-reductase expression in rat tissues.ical inactivation of 4-ene-3-ketosteroids, mainly adrenal corticosteroids (19).Previous biochemical studies of 5a-reductase have revealed kinetic parameters, such as affinity constants to steroid hormones, as well as the enzyme subcellular distribution in the rough endoplasmic reticulum and/or nuclei of various tissues (1,(20)(21)(22)(23)(24). Because the activity of Sareductase is extremely unstable in cell-free preparations (1, 20), it has not been purified, and therefore the regulation of its expression could not be studied at the molecular level. To approach this issue, we pursued an experimental model in which 5a-reductase biosynthesis can be studied in intact living cells. Toward this aim, we designed a bioassay for the detection of newly synthesized 5a-reductase produced in mRNA-microinjected Xenopus oocytes. The oocytes efficiently translate microinjected heterologous mRNA, perform correct posttranslational processing and, most importantly for 5a-reductase, direct newly synthesized proteins into the correct subcellular compartments (for review, see ref. 25).Here, we report that Xenopus oocytes are able to synthesize catalytically active 5a-reductase, directed by microinjected poly(A) + RNA prepared from female and male rat liver. For yet unknown reasons, there are remarkable differences between the specific activities of 5a-reductase in female liver, male liver (16, 17)...

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“…Hence, the differential effects of T and DHT on 5 -R1 found in the present study cannot be attributed solely to the conversion of T to estradiol but rather indicate a sexually dimorphic regulation of the enzyme. b) The possible metabolism of DHT into inactive 3 -androstanediol (3 -Diol) or active 3 -androstanediol (3 -Diol), as occurs in the pituitary (Denef et al 1974). In general, reduction at the C3 position decreases the binding affinity to intracellular receptors (Negri-Cesi et al 1996) such as AR.…”

Section: Discussionmentioning

confidence: 99%

Steroid 5α-reductase isozymes in the adult female rat brain: central role of dihydrotestosterone

Torres

Ortega

2006

Journal of Molecular Endocrinology

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The enzyme 5 -reductase (5 -R) (EC 1·3·99·5) exists as two isoforms, 5 -R type 1 (5 -R1) and 5 -R type 2 (5 -R2). 5 -R1 has been associated with catabolic functions whereas 5 -R2 has been associated with sexually dimorphic functions of the male. We recently demonstrated that both 5 -R isozymes are present in the central nervous system (CNS) of the adult male rat and are regulated in an opposing way by androgens. This finding raises the question as to whether both isozymes play a role in the sexual dimorphism of the CNS, besides other functions. To test this hypothesis, it is essential to study the regulation of both isozymes by androgens in the female. In this work, we studied the effects of testosterone (T) and dihydrotestosterone (DHT) on mRNA levels of both 5 -R isoforms in the prefrontal cortex of the adult female rat by one-step quantitative RT-PCR coupled with laser-induced fluorescence capillary electrophoresis. Our results demonstrate for the first time that 5 -R2 mRNA is slightly regulated by T and DHT in females. Surprisingly, 5 -R1 mRNA is not regulated by T in the intact female, whereas it is very positively regulated by DHT, a more potent androgen than T. These data indicate the great sexual dimorphism in the CNS with respect to both 5 -R isozymes, and suggest a crucial role of DHT in the sexual dimorphism of the CNS in the female. These results open up a new research line that may lead to a better understanding of the physiology of the CNS.

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Sex-Dependent Changes in Pituitary 5α:-Dihydrotestosterone and 3α-Androstanediol Formation During Postnatal Development and Puberty in the Rat

Cited by 89 publications

References 0 publications

Evidence that Pituitary 5<i>α</i>-Dihydrotestosterone Formation is Regulated through Changes in the Proportional Number and Size of the Gonadotrophic Cells

Evidence that Pituitary 5<i>α</i>-Dihydrotestosterone Formation is Regulated through Changes in the Proportional Number and Size of the Gonadotrophic Cells

Biosynthesis of catalytically active rat testosterone 5 alpha-reductase in microinjected Xenopus oocytes: evidence for tissue-specific differences in translatable mRNA.

Steroid 5α-reductase isozymes in the adult female rat brain: central role of dihydrotestosterone

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