Regulation of formation in vivo of pyridoxal phosphate in hydrazine-treated rats.

The formation in vivo of pyridoxal phosphate was studied in hydrazine-treated rats. hydrazine was administered i.p. at a dose of 1.28 mg/day (20% LD50) for each 100 g body weight for 7 days. Hydrazine administered at the present dose did not appear to have an effect on the pyridoxal phosphate level of either liver on kidney tissue. Hydrazine treatment, however, elevated the pyridoxal level in liver, while kidney pyridoxal level remained unaltered under the same condition. The pyridoxine phosphate oxidase activity in liver, unlike that in kidney, was found to be increased after hydrazine treatment. The increase in pyridoxine phosphate oxidase activity in the liver of hydrazine-treated rats was prevented by actinomycin D treatment. It has been suggested that hydrazine treatment at the present dose enhanced the rate of formation of pyridoxal phosphate from pyridoxine-5-phosphate in liver, while the formation of pyridoxal phosphate in kidney appeared to be independent of hydrazine treatment. The increased activity of liver pyridoxine phosphate oxidase in hydrazine-treated rats was ascribed to the induction of the enzyme. It has been further suggested that the unalteration in the liver pyridoxal phosphate level in hydrazine-treated rats inspite of enhanced conversion of pyridoxine-5-phosphate to pyridoxal phosphate, was probably caused by the increased hydrolysis of pyridoxal phosphate.