| Abstract | The biosynthesis of non-aromatic 19-norsteroids has been studied using primary cultures of porcine granulosa cells. Formation of 5(10)-estrene-3β,17β-diol, a novel 19-norsteroid, from androstenedione and 19-hydroxyandrostenedione by porcine granulosa cells is reported for the first time. The structure was deduced from (i) comparison of its elution times on C18 reverse phase HPLC with authentic 5(10)-estrene-3β,17β-diol (ii) identification with 5(10)-estrene-3β,17β-diol-diacetate after acetylation (iii) oxidation/acid catalysed isomerization to 19-norandrostenedione. Serum or serum plus FSH significantly stimulated (seven fold increase) formation of 5(10)-estrene-3β,17β-diol from androstenedione and 19-hydroxyandrostenedione. Formation of 5(10)-estrene-3β,17β-diol from both substrates was significantly (p<0.01) reduced by the aromatase inhibitors 4-hydroxyandrostenedione (15 μM) and aminoglutethimide phosphate (10−4M). These results suggest that 5(10)-estrene-3β,17β-diol (and 19-norandrostenedione) may be formed by enzymes similar to the aromatase complex required for estradiol-17β biosynthesis. 5(10)-Estrene-3β,17β-diol is converted by granulosa cells to four metabolites. 19-Norandrostenedione was identified by crystallization to constant specific activity; 19-nortestosterone is a minor product. Production of 19-norandrostenedione and 19-nortestosterone indicates that granulosa cells possess the enzymes necessary for the transformation of 5(10)-estrene-3β,17β-diol and other 3-hydroxy-5(10)-estrenes to 19-nor-4-ene-3-ketosteroids. The formation of 5(10)-estrene-3β,17β-diol and 19-norandrostenedione as substantial metabolites of androstenedione suggest a physiological role for these 19-norsteroids in ovarian follicular development. |
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