Effect of growth hormone and ectopic transplantation of pituitary gland on sex-specific forms of cytochrome p-450 and testosterone and drug oxidations in rat liver

The effects of growth hormone and ectopic transplantation of pituitary gland on the amounts of sex-specific cytochrome P-450, P-450-male and P-450-female, and the activities of testosterone and drug hydroxylases in male rat liver microsomes were studied. Hypophysectomy decreased the content of P-450-male, without changing the total cytochrome P-450 level. The continuous infusion of growth hormone into hypophysectomized rats and the transplantation of pituitary gland under the renal capsule caused a further decrease in P-450-male content and an expression of P-450-female. In contrast, the intermittent injection of growth hormone into hypophysectomized rats increased P-450-male content to the level seen in intact male rats. The activities of testosterone 2α- and 16α-, but not 6β-, 7α-, or 15α-hydroxylase, were changed in association with the level of P-450-male by these treatments. Anti-P-450-male immunoglobulin G inhibited testosterone 2α-and 16α-hydroxylations, but not 6β-, 7α- or 15α-hydroxylation. These results indicate that growth hormone regulates the expression of P-450-male responsible for testosterone 2α- and 16α-hydroxylations. The metabolism of 7-propoxycoumarin, benzo(a)pyrene and aminopyrine also changed with the content of P-450-male, although the correlation was less than that observed with testosterone 2α- and 16α-hydroxylation.