Abstract

• Cytochrome P-450 is sometimes called the microsomal carbon monoxide-binding pigment. It is present in the microsomal fraction of several animal tissues, and also in the mitochondrial fraction of adrenal cortex, but not in the mitochondria of other tissues. Cytochrome P-450, the liver microsomal drugmetabolizing enzyme is membranebound and fraction as multicomponent electron transport system for the metabolism of a variety of endogenous substrates(such as steroids, fatty acids, and bile acids) and exogenous substance (such as drugs, carcinogens, insecticides, and many other foreign compounds). The effect estrous cycle and preimplantation on the levels of hepatic microsomal cytochrome P-450 in mice were determined. In effect of estrous cycle on microsomal cytochrome P-450 level, the most increment was at estrus. The content of cytochrome P-450 was increased significantly at pregnant Day 3 of preimplantation.