The levels of hepatic microsomal cytochrome P-450 in preimplantation rats were determined 1) The activities of the hepatic microsomal cytochrome P-450 associated with the events leading to implantation were gradually increased in preimplantation rats. 2) The level of the hepatic microsomal cytochrome P-450 was peak, 2.65 nmoles/mg protein, on day 4 in normal preimplantation rat. 3) The activity of the hepatic microsomal cytochrome P-450 was decreased in ovariectomized rat than normal rat. 4) The hepatic microsomal cytochrome P-450 level in ovariectomized rat was peak, 2.39 nmoles/mg protein, on day 5. 5) We observed the fact thar the activity of microsomal P-450 was delayed in ovariectomized rat. 6) We confirmed the fact that the hepatic microsomal cytochrome P-450 level was affected by steroid hormone.

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.

Cytochrome P-450 is a terminal oxidase of the hepatic microsomal monooxygenase system associated with the oxidative biotransformation of a varity of lipophilic endogenous and exogenous compounds, and generally is assayed by CO-binding spectro-photometry of dithionite-reduced samples. In well fed normal male rats with or without stress condition, the dffect of antiulcer drug; cimetidine, sulpiride and diazepam on the level of microsomal cytochrome P-450 were determined. Only stress condition produced on significant effect in cytochrome P-450 contents. Administration of cimetidine, sulpiride and diazepam in this condition caused a 44.1%~87.5% increment in cytochrome P-450, diazepam produced the most increase. After diazepam treatment of rats, the peak position of cytochrome P-450 shifted to a longer wave length of 452 nm.

Total cholesterol content of fishes and shellfishes, which bought in the local market, was estimated in part (head, muscle, skin, egg, and roe). and also, the general analytical data(water, protein, fat, and ash) were examined in the parts. The results of cholesterol content are as follows;

1) In the fresh water fishes, the cholesterol content was highest in trout and watereel.

2) In the marine fishes, it was high in makerel, Spanish makerel, horse makerel, and hickory sard and low in sea-cucumber and thormbock stingray.

3) Cholesterol content of the parts in both fresh water fishes and marine fishes was highest in roe, and the next egg, skin, head, and muscle in the ordet named.

4) Cholesterol content of the shell fishes was 100mg~200mg/100g.

5) Generally, the cholesterol content also was high in the sample that fat content was high.