Suppression of altered hepatic foci development by a high fish oil diet compared with a high corn oil diet in rats

Effects of low corn oil high corn oil, and high fish oil diets on altered h epatic foci development in female Sprague-Dawley rats were investigated. Ra ts assigned to Groups 1-4 were initiated with saline as the control and tho se assigned to Groups 5-7 were initiated with diethylnitrosamine (DENIS mg/ kg) at 24 hours of age. After weaning, all rats, except those in Group 1, r eceived 500 ppm phenobarbital (PB) in their diet as tumor promoter for thre e months. Altered hepatic foci development was significantly lower in DEN-i nitiated rats fed the high fish oil + PB diet than in DEN-initiated rats fe d the high corn oil + PB diets. Liver weight and relative liver weight were significantly greater in rats fed the high fish oil + PB diet than in rats fed the other diets, and hepatic biotransformation/detoxification enzyme a ctivities were greater in rats fed the fish oil + PB diets than in rats fed the other diets. These results suggest that the effect of a high fish oil diet on altered hepatic foci may occur through regulation of hepatic biotra nsformation/detoxification enzyme activities, leading to alteration in the tumor-promoting action of PB. Dietary lipid significantly affected the hepa tic phospholipid fatty acid composition of rats. n-3 polyunsaturated fatty acids were incorporated into membrane phospholipid at the expense of nd pol yunsaturated fatty acids. A high fish oil diet caused greater oxidative str ess in rats, as measured by plasma vita-min E level, red blood cell glutath ione status, liver lipid peroxidation, and hepatic glutathione reductase ac tivity. Pearson's correlation analysis indicated that the foci number was n egatively correlated to the liver thiobarbituric acid-reactive substance an d 7-pentoxyresorufin O-dealklase activity, and the foci area was negatively correlated to the liver thiobarbituric acid-reactive substance activity (p < 0.05) in rats of groups that developed foci. These results suggest that the type of dietary lipid is the more important determinant for gamma -glut amyl transpeptidase-positive foci development than tire amount of dietary l ipid when rats consumed approximately the same amount of calories in all th e dietary groups, and the underlying mechanisms may be partially ascribed t o the antioxidant/oxidation status and biotransformation/detoxification sys tem of rats.