ABSTRACT
The development and sexual differentiation of 11β- and 17β-hydroxysteroid dehydrogenase activities was investigated in the liver, kidney, adrenal and gonads of rats over a period of 15–120 days of life.
11β-Hydroxysteroid dehydrogenase in the adrenal and ovary was at the limit of detectibility at all the stages of life investigated. In the liver, kidney and testis the enzyme activity is restricted to the microsomal fraction and demonstrates an age-dependent development; in the liver, kidney and in the gonads it is additionally characterized by a sexual differentiation to higher values in the male sex.
In all the organs investigated the cytoplasmic and microsomal fractions contain 17β-hydroxysteroid dehydrogenase activity; the activities are very low in the microsomal fraction of the kidney and in the cytosol of the testis. In all the organs the enzyme activity of at least one cell fraction displays an age-dependent development. The only activities, not demonstrating an ontogenesis are those of the cytosol of the adrenal and those of the microsomal fraction of the kidney. The age-dependent development is accompanied by a sexual differentiation of the enzymes activities. The only exception is the microsomal activity of the liver. The female sex shows the higher activity in the kidney, adrenal and gonads; whereas the male animal shows the higher activity only in the cytosol of the liver.
The developmental processes of 11β- and 17β-hydroxysteroid dehydrogenase have the following properties in common:
In the immature phase (day 15–30) the activities of the enzymes develop either very rapidly to manifold higher values or remain constant at the low neonatal level; no sexual differentiation of the enzymes activities occurs at this stage of life. The rapid increase in activity is found only in the liver and kidney, that is in the steroid hormone catabolizing organs. It does not occur in the steroid hormone producing glands.