Synthesis of pheromone precursors in human testes

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Differential

metabolism of pregnenolone by testicular homogenates of humans and two species of macaques. Lack of synthesis of the

human sex pheromone precursor 5,16-androstadien-3 beta-ol in nonhuman primates.


Weusten JJ, van der Wouw MP,

Smals AG, Hofman JA, Kloppenborg PW, Benraad TJ.

Department of Medicine, St. Radboud Hospital, University of

Nijmegen, The Netherlands.

In previous reports we described the early time sequence in in vitro [4-14C]

pregnenolone metabolism in human and rat testicular homogenates and, apart from a difference in the preferred route

of the conversion of pregnenolone to testosterone, we demonstrated the presence of delta 16-synthetase activity in

human but not in rat testes. In the study of testicular function higher monkeys are increasingly used as a model for

human reproduction. The availability of testes from 2 different species of macaques (rhesus and crab eating monkeys)

enabled us to compare the in vitro metabolism of pregnenolone in these testes with human testes. The pattern

obtained in both monkey species were very similar, but completely different from those found in man. The delta 4

pathway was the preferred route for the conversion of pregnenolone to testosterone in the monkeys tested, the delta

5 pathway in the humans. delta 16-Synthetase activity, a prerequisite for the synthesis of the sex pheromone

precursors 5,16-androstadien-3 beta-ol and 4,16-androstadien-3-one, was clearly measurable in the human but not in

the monkey testicular homogenates. So far, man and boar are the only species harbouring delta 16-synthetase activity

in their testes. These in vitro data indicate that the nonhuman primates studied are not suitable models for the

study of human testicular function.

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