The time course of the effect of hypophysectomy and oestrogen treatment on the hepatic metabolism of androst-4-ene-3,17-dione in male and female rats

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Abstract
Hypophysectomy of male animals has little effect on the hepatic androst-4-ene-3,-17-dione (androstenedione) metabolism, except for possible changes in the kinetics of the 16.alpha.- and 7.alpha.-hydroxylases. Hypophysectomy of female animals leads to a masculinization of hepatic androstenedione metabolism, following the changes seen in Vmax of the enzymes involved, probably due to the removal of the source of feminizing factor thought to maintain the female type of metabolism in the liver. There seems to be a temporal dissociation of the effects on the various enzymes, indicating different cellular control mechanisms for these enzymes. Estrogen treatment of male rats causes feminization of the hepatic androstenedione metabolism. The time study shows an initial increase in 17-hydroxysteroid oxidoreductase and 6.beta.- and 16.alpha.-hydroxylase activities, followed by a decrease in the values in females. This biphasic effect is possibly due to an initial direct effect via the hypothalamo-pituitary system.