Structural and regulatory analysis of the male-specific rat liver cytochrome P-450 g: Repression by continuous growth hormone administration

Complementary DNA clones encoding the male-specific rat liver cytochrome P-450 g have been isolated by cross-hybridization with sequences from the female-specific rat liver cytochrome P-450 15β. Tissue distribution analysis indicates the liver as the organ with major expression of this cytochrome P-450 gene. Minimal P-450 g expression was also detected in prostate, kidney, heart, and brain. A developmental analysis reveals liver expression in the 8-week-old male and to a lesser extent in the 4-week-old male, but no detectable expression is seen in females of these ages or in 1- and 2-week-old rats from both sexes. Hypophysectomy of female rats dramatically increases hepatic expression of P-450 g, whereas continuous GH administration represses hepatic expression in male or female hypophysectomized rats. In similarity to P-450 15β and P-450 16α, therefore, the cytochrome P-450 g gene in liver is GH regulated.