Steroids and the maturation of rat tissues

In normal developing rats there are two periods when glucocorticoids exert important influences upon hepatic chemical differentiation: new enzymes appear in liver after the late fetal and also after the postnatal (2nd week) upsurge of plasma corticosterone. Cortisol, administered prior to the natural increase in endogenous corticosterone, induces these enzymes before the scheduled time. Such interference also causes premature losses in enzymes (in various organs) which appear to be more important to growth per se than to tissue-specific metabolic functions. Current hypotheses about the mechanism of hormone action are inadequate to explain the fact that glucocorticoids, even in the same tissue, induce different enzymes at different stages of development. Several observations suggest that the competence of different synthetic systems to respond to a hormonal trigger develops in distinct steps, under the impact of additional, specific stimuli.