Androgen responsiveness of the liver of the developing rat.

The activities of the hepatic microsomal 2alpha-, 2beta-, 7alpha- and 18-hydroxylase systems active on 5alpha-[4-(14)C]androstane-3alpha,17beta-diol were studied in male and female rats which had been castrated at birth and at the age of 7, 13, 21, 27, 34, 43 and 55 days, treated for 5 days with 2mg of testosterone propionate/kg body weight and killed 6 days after castration. The 7alpha-hydroxylase system was affected very little by androgen treatment at all stages during development. On the other hand it was found that the rat liver passed through three phases during development with respect to androgen responsiveness as judged by changes in the activities of the 2alpha, 2beta- and 18-hydroxylase systems: a first phase (from the neonatal period up to about 19 days of age) with a relative androgen unresponsiveness in both male and female rats, a second phase (from about 27 to about 33 days of age) when male and female rats responded equally well to androgens and a final phase (from about 40 days of age) with a successively decreasing androgen responsiveness in female rats but with a retained responsiveness in male rats. The hypothesis is presented that neonatal imprinting of the liver by testicular androgen(s) determines the development and degree of androgen responsiveness of liver tissue in the rat.