Effect of several xenobiotics on the activities of enzymes affecting ascorbic acid synthesis in rats

The dietary addition of several xenobiotics, such as PCB, DDT, aminopyrine, chloretone, BHT and BHA, caused significant increases in the ascorbic acid in urine and liver of rats. The administration of all types of xenobiotics used in the present experiments increased the activity of hepatic UDP-glucose dehydrogenase (1.3-2.8-fold), and the administration of PCB, DDT, BHT or BHA significantly increased the activity of hepatic UDP-glucuronyl transferase (2.2-13.1-fold). The activity of beta-glucuronidase was slightly increased with feeding of PCB, DDT, chloretone or aminopyrine. However, the activity of hepatic UDP-glucuronic acid pyrophosphatase, the conversion of D-glucuronic acid or D-glucuronolactone into L-ascorbic acid and the activity of hepatic L-gulonolactone oxidase did not increase with the administration of PCB or DDT. It is suggested that the increases in the activities of UDP-glucose dehydrogenase and UDP-glucuronyl transferase would have a major role in the stimulation of ascorbic acid synthesis in xenobiotic treated rats.