In Vitro Metabolism of3H-Pregnenolone and3H-Progesterone by Adult and Prepubertal Human Testicular Tissue Before and During Gonadotrophic Treatment

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Abstract
The in vitro conversion of tritiated pregnenolone and progesterone was studied in testicular tissue from three infertile adult males before and during 25-30 weeks of theapy with hCG alone or combined with hMG. Furthermore, the in vitro conversion of pregnenolone was studied in testicular tissue from five prepubertal boys with undescended testes, two of whom had been subjected to hCG treatment for 5 weeks. The gonadotrophic treatment appeared to augment the steroid conversion mediated by the enzymes 3β-hydroxysteroid dehydrogenase and 17α-hydroxylase in adult as well as prepubertal testicular tissue. The coversion mediated by C17-20-lyase along the δ4 metabolic pathway was not increased, causing a “trap” along the δ4 metabolic pathway. The increased production of testosterone in vitro from tritiated pregnenolone, which was observed during gonadotrophic treatment, probably took place along the δ5 metabolic pathway through the C17-20-lyase step, whereas C21 steroids converted to the δ4 metabolic pathway were found to be “trapped” as 17α-hydroxyprogesterone.

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