Altered distribution of constitutive forms of microsomal cytochrome P-450 in tumor-bearing mouse liver.

Abstract

Changes of microsomal cytochrome P-450 species in the livers of mice were examined after the inoculation of Ehrlich ascites tumor cells i.p. into male ddY mice. The total content of hepatic cytochrome P-450 was observed to decrease around 6 days after the tumor-inoculation and reached the level of 40 to 50% of those of control mice (27.8 nmol P-450/g of control liver) after 10 days, while the liver weights of tumor-bearing mice slightly increased even at the end of the 2nd week. Microsomal proteins of tumor-bearing mice remained at the level of around 80% of control livers at the end of the 2nd week. The activity of 7-ethoxycoumarin deethylation decreased roughly in proportion to the content of microsomal cytochrome P-450. On the contrary, the specific activity of benzphetamine N-demethylase per nmol of P-450 in the tumor-bearing mouse liver increased to more than 2 fold of the value of normal liver (25 nmol HCHO/nmol P-450/min for control liver) during the last stage of the second week. These results suggest that the reduction of individual forms of cytochrome P-450 in the tumor-bearing mouse liver was not random and a new steady state of distribution of these hemeproteins was established under the pathological conditions.