Cytochrome P-450 as a determinant of sex difference of drug metabolism in the rat.

1. Recent advances in the studies of sex-related differences of drug metabolism in the rat are described. Experiments with novel substrates have provided new insights into the sex differences of drug metabolism. 2. One of each form of cytochrome P-450, P-450-male and P-450-female, from liver microsomes of male and female rats, respectively, were purified to electrophoretic homogeneity. 3. These forms of cytochrome P-450 are distinguishable from each other in their catalytic, physical and immunochemical properties. 4. The use of antibodies to the two forms of cytochrome P-450 shows that P-450-male and P-450-female, present in rat-liver microsomes, are dependent on sex hormones. 5. In addition, evidence for the involvement of multiple forms of cytochrome P-450 in the occurrence of the sex difference has been presented.