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Abstract

Opposing changes in 3a-hydroxysteroid dehydrogenase oxidative and reductive activities in rat Leydig cells during prepubertal development (PDF) (HTML) 
Ge,Renshan; Hardy,Dianne O.; Catterall,James F.; Hardy,Matthew P.
Biology of Reproduction 60 855-860
Publication date: 1999

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The enzyme 3-hydroxysteroid dehydrogenase (3-HSD) has an importantrole in androgen metabolism, catalyzing the interconversionof dihydrotestosterone (DHT) and 5-androstane-3,17ß-diol(3-DIOL). The net direction of this interconversion will affectthe amount of biologically active ligand available for androgenreceptor binding. We hypothesize that in Leydig cells, differentialexpression of 3-HSD enzymes favoring one of the two directionsis a mechanism by which DHT levels are controlled. In orderto characterize 3-HSD in rat Leydig cells, the following propertieswere analyzed: rates of oxidation (3-DIOL to DHT) and reduction(DHT to 3-DIOL) and preference for the cofactors NADP(H) andNAD(H) (i.e., the oxidized and reduced forms of both pyridinenucleotides) in Leydig cells isolated on Days 21, 35, and 90postpartum. Levels of 3-HSD protein were measured by immunoblottingusing an antibody directed against the liver type of the enzyme.Levels of 3-HSD protein and rates of reduction were higheston Day 21 and lowest on Day 90. The opposite was true for therate of 3-HSD oxidation, which was barely detectable on Day21 and highest on Day 90 (59.08 ± 6.35 pmol/min per 10cells, mean ± SE). Therefore, the level of 3-HSD proteindetectable by liver enzyme was consistent with reduction butnot with oxidation. There was a clear partitioning of NADP(H)-dependentactivity into the cytosolic fraction of Leydig cells, whereason Days 35 and 90, Leydig cells also contained a microsomalNAD(H)-activated 3-HSD. We conclude that 1) the cytosolic 3-HSDin Leydig cells on Day 21 behaves as a unidirectional NADPH-dependentreductase; 2) by Day 35, a microsomal NAD(H)-dependent enzymeactivity is present and may account for predominance of 3-HSDoxidation over reduction and the resultant high capacity ofLeydig cells on Day 90 to synthesize DHT from 3-DIOL.

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