Studies on the possible mechanism of hydrazine action on ascorbic acid-metabolising enzymes.

The activities of enzymes associated with the synthesis and degradation of L-ascorbic acid were studied in hydrazine-treated rats supplemented with pyridoxine. The effects of hydrazine in vitro were also examined on these enzymes. The activity of liver D-glucuronoreductase was reduced in hydrazine-treated rats even after receiving pyridoxine in excess. But, the decreased activities of liver and kidney dehydroascorbatases in hydrazine-treated rats were reversed by pyridoxine supplementation. Hydrazine in vitro could not inhibit the activity of liver D-glucuronoreductase or L-gulonooxidase. The drug was also unable to inhibit in vitro the activity of liver and kidney dehydroascorbatases. Studies with dialyzed liver homogenates showed that the diminished activity of D-glucuronoreductase in the liver of hydrazine-treated rats was maintained even after dialyzing the tissue preparations. In contrast, the reduced activity of dehydroascorbatase in the liver of hydrazine-treated rats was abolished following dialysis of the liver preparations. It has been suggested that the diminished activity of liver D-glucuronoreductase after hydrazine treatment might arise from the reduced synthesis of enzyme protein, while the reduction in the activity of dehydroascorbatase following hydrazine treatment could be ascribed to depletion in vivo of pyridoxal phosphate and/or to the involvement of some dialyzable factors.