Liver microsomal mixed-function oxidases in response to dietary n-3 fatty acid levels in rats.

Phenobarbital (PB)-induced activities of the liver microsomal mixed-function oxidase (MFO) system in response to dietary levels of n-3 fatty acids were investigated in rats. The MFO activities were assessed by the contents of cytochromes P-450 and b5, and the activities of NADPH-cytochrome c reductase, aminopyrine N-demethylase and aniline hydroxylase. A linoleic acid (C18:2, n-6; LA) diet (2.0 energy % as LA) and n-3 fatty acid diets (0.3, 1.0, 1.9 or 4.8 energy % as n-3 fatty acids) were fed to rats for 16 days. The activities of MFOs except that of NADPH-cytochrome c reductase increased, as compared with the LA diet, with increasing the dietary n-3 fatty acid level, concomitant with the increase in n-3 fatty acids and decrease in n-6 fatty acids in liver microsomal lipids. The dietary LA over 1.8 energy % up to 13.8% did not increase the activities of PB-induced MFOs. Consequently, dietary n-3 fatty acids further elevated the PB-induced MFO activities effectively. These results suggest a differential response of dietary n-6 and n-3 fatty acids to the PB-induced MFO activities.