Effect of dietary quality of protein on liver microsomal mixed function oxidase system, plasma cholesterol and...

Exposure of rat to polychlorinated biphenyls (PCB) results in an increase in activity of liver microsomal mixed function oxidase system, plasma cholesterol and urinary ascorbic acid. Experiments were designed to study the effect of dietary quality of protein on these metabolic responses to dietary addition of PCB. The diets contained either whole egg protein, casein, fish protein, soy protein, soy protein plus 0.34% methionine, wheat-gluten, corn-gluten or gelatin fed at 10% of the diet. In general, the relative biological values of proteins as shown by the gains in body weight were positively correlated with activity of the microsomal enzyme system including aminopyrine N-demethylase, aniline hydroxylase, cytochrome P-450 and NADPH-cytochrome c reductase, plasma level of cholesterol and urinary ascorbic acid. Supplement of methionine to soy protein diet containing PCB caused a significant increase in liver and plasma cholesterol and in urinary ascorbic acid, although the influence on the microsomal enzyme system was slight. The gelatin diet containing PCB gave higher activity of the enzyme system than that expected from the biological value, although the same protein diet without PCB caused quite low activity as expected from the biological value.