Effect of pyridoxine administration on the induction of cytosolic aspartate aminotransferase in the liver of rats treated with hydrocortisone.

The effects of pyridoxine and hydrocortisone administrations on the rate of synthesis of cytosolic aspartate aminotransferase in adrenalectomized pyridoxine-deficient rat livers were examined. Induction of cytosolic aspartate aminotransferase by hydrocortisone was observed 6 to 10 h after the injection. Treatment with pyridoxine daily for 6 days but not for the 2 days, resulted in suppression of the enzyme synthesis. Similar suppression of enzyme synthesis was observed in rats without hydrocortisone treatment. The activity of tryptophan oxygenase, which is known to be induced by glucocorticoid and does not contain pyridoxal phosphates, was higher in the livers of pyridoxine-deficient rats than in that of controls. The possible effects of pyridoxal phosphate on the action of glucocorticoid are discussed based on the results.