Effects of some xenobiotics on ascorbic acid metabolism in rats

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.