Effects of 0.03% polychlorinated biphenyls (PCB) in the diet and various dietary fibers [konjac mannan (KM), pectin, sodium carboxymethyl cellulose (CMC) and cellulose] at a 5% level in the diet on serum and liver lipid metabolism and urinary ascorbic acid were studied. A comparison between dietary PCB and 1% cholesterol in the diet was also made. Serum albumin, protein, total and high density lipoprotein (HDL)-cholesterol, triglyceride, urinary and liver ascorbic acid, liver cholesterol and total lipids were increased in rats fed PCB. Pectin or KM depressed the elevation in serum protein, total and HDL-cholesterol, triglyceride and liver lipids due to PCB intake. Cellulose or CMC had no significant effect on these indices. Urinary ascorbic acid was not decreased by these dietary changes. Serum total cholesterol and low density lipoprotein (LDL) plus very low density lipoprotein (VLDL)-cholesterol, and liver total lipids, and cholesterol were significantly higher, and serum HDL-cholesterol and triglyceride were significantly lower in the cholesterol-fed group as compared to PCB-fed rats. Addition of KM to a cholesterol diet significantly depressed serum total cholesterol and LDL plus VLDL-cholesterol, liver cholesterol and total lipids. It seems likely that cholesterol metabolism is quite different during dietary PCB and cholesterol feeding.

The administration of xenobiotics, PCB, DDT, or aminopyrine to rats causes a marked increase in urinary excretion of ascorbic acid and in various tissue levels of ascorbic acid. When rats were fed diet containing 200 ppm PCB or 500 ppm DDT (14 days), the incorporations from D-(U-14C) glucose into ascorbic acid in liver were significantly increased. The dietary addition of 200 ppm PCB, 500 ppm DDT, 2,000 ppm pentobarbital or 3,000 ppm chloretone caused a significant increase in the activity of hepatic UDPglucose dehydrogenase, but did not affect the activity of hepatic L-gulonolactone oxidase. Good correlation between the liver level of ascorbic acid and the activity of hepatic UDPglucose dehydrogenase was observed. Subsequently, in rats fed the basal diet (30% casein diet) or the diet containing 200 ppm PCB, the specific activities of ascorbic acid in urine and in various tissues were measured 6 hours, 12 hours and 24 hours after the oral administration of L-(l-14C)ascorbic acid. Dietary PCB accelerated the disappearances of radioactivities in ascorbic acid in urine and various tissues, that is, shortened the half lives of radioactivities in ascorbic acid. It is likely that the administration of xenobiotics, such as PCB or DDT, to rats increases the biosynthesis of ascorbic acid and accelerates concomitantly the turnover of ascorbic acid in body.

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