Effect of dietary level of protein on liver microsomal drug-metabolizing enzymes, urinary ascorbic acid and lipid metabolism in rats fed PCB-containing diets.

Effects of dietary level of protein on liver microsomal drug-metabolizing enzyme system, lipids and urinary ascorbic acid metabolism were studied in the rats fed 0.1% polychlorinated biphenyl (PCB) containing diets. In the rats not receiving PCB, the activity of the enzyme system increased as the protein level was increased up to around 35%. In a short-term experiment (8-9 days), dietary PCB caused an increase in the activity of the enzyme system regardless of dietary level of protein. In a semi-long term experiment (29-30 days), however, 35-55% protein diets did not allow for induction to the same extent. As a result the highest activity was observed with 10-20% protein diets in this period. The increments in urinary ascorbic acid and in serum cholesterol were generally potentiated with high-protein diets. Maximum increments in urinary ascorbic acid and serum cholesterol were obtained with 20% protein and 35% protein, respectively, in the semi-long term experiment. In contrast to serum cholesterol, the accumulation of liver cholesterol and triglyceride due to PCB was markedly potentiated with low-protein diets.