Effect of polychlorinated biphenyls on lipids and ascorbic acid metabolism in streptozotocin-induced diabetic rats

Metabolic changes in lipids, ascorbic acid, and hepatic microsomal cytochrome P-450 by feeding polychlorinated biphenyls (PCB) were investigated in streptozotocin-induced diabetic rats. Streptozotocin (STZ, 60 mg/kg body weight) was injected in Wistar male rats intraperitoneally. Diabetic and non-diabetic rats were fed ad libitum a 20% casein-based control diet or a PCB-containing diet (200 mg/kg diet) for 9 days. Body weight decreased significantly in STZ-induced diabetic rats with or without PCB (groups PD and D, respectively). In rats of group D, urinary ascorbic acid excretion was 15 times higher than that in non-diabetic rats fed a control diet (group C). Dietary PCB caused 30-fold higher urinary ascorbic acid excretion in non-diabetic rats (group P) than that in group C. In group PD, urinary ascorbic acid was nearly 60 times higher than that in group C. Ascorbic acid in liver and kidney was significantly lower in group D than in group C, and it was significantly lower in group PD than in group P. Liver microsomal cytochrome P-450 and b5 were both increased by dietary PCB in group P. Addition increase in these enzymes was observed in diabetic rats by PCB. Serum total cholesterol was 1.8 times higher in group P than in group C. Further increase in serum total cholesterol was observed in group PD. These data suggest that metabolic changes in lipids and ascorbic acid induced by the dietary xenobiotic were magnified in STZ-induced diabetic rats.