Effects of pyridoxine deficiency on the metabolism of N-nitrosodimethylamine in the rat.

The alteration in the metabolic activation of N-nitrosodimethylamine (NDMA) was investigated in the rat during dietary pyridoxine deficiency. The in vitro metabolism of NDMA by demethylase system was measured in both liver and kidney microsomes. The profile of the kidney enzyme appears similar to that of the liver indicating that at least two forms of isozymes with the low and the high Km's are present. Pyridoxine deficiency significantly increased the activity of NDMA-demethylase of both organs. The increase in the activity of NDMA-demethylase induced by dietary pyridoxine deficiency can be reversed by supplementation of pyridoxine (500 micrograms), i.p., daily for two consecutive days. The increase in the NADPH cytochrome c reductase activity was observed after 6 weeks on pyridoxine-deficient diet.