Steroids and Induction

Physiologically, microsomal oxidation via the cytochromes appears to serve for the lipophilic oxidation of steroids, fatty acids, heme, and drugs. The microsomal cytochromes and smooth endoplasmic reticulum may be controlled in part by steroids. For example, the relatively high production of heme by normal liver suggests that there may be natural 5/i-H steroids that normally serve to maintain a certain rate of heme synthesis by inducing the synthesis of ALA-synthetase. An 

The glucocorticoids may be involved in induction of a number of enzymes by changing the mRNA s, as suggested by the studies of Drews and Brawerman [123]. Using DNA-RNA hydridization, they observed that, 3 hours after hydrocortisone had been administered to adult rats, the mRNA s of the liver were altered, implicating an early selective effect of the hormone on the synthesis of mRNA s coding for the relatively few enzymes that were induced. 

A different interpretation of glucocorticoid action on the induction of liver tyrosine amino transferase has been suggested. Tomkins et al. [131] propose that the steroid acts not at the transcriptional but rather at the translational level to inhibit the action of a repressor on the synthesis of the enzyme. 

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