Regulation of ornithine aminotransferase in rat kidney by estradiol and pyridoxine.

Increased synthesis of ornithine aminotransferase [EC 2.6.1.13] (OAT) in the kidney of pyridoxine-deficient rats has been reported previously (Ikeda, M. and Okada, M. (1985): J. Nutr. Sci. Vitaminol., 31, 553-561). In this report the effects of 3,3',5'-triiodothyronine (T3) and estradiol on OAT activity in the kidney of rats given pyridoxine-deficient and control diets were studied. T3 induced renal OAT activity in rats given the control diet but not in those given the pyridoxine-deficient diet. On the other hand, estradiol induced renal OAT activity in both deficient and control rats, the levels induced in the two groups being the same. Maximal induction of OAT occurred at a lower dose of estradiol in pyridoxine-deficient rats than in the controls. When rats fed on pyridoxine-deficient diet were pretreated with pyridoxine for several days, OAT induction by estradiol was suppressed. Thus pyridoxal phosphate (PLP) may modulate OAT activity in rat kidney through the action of estradiol.