Differential effects of sex steroids on uterine and renal ODC activity in ovariectomized rats

Many hormones are known to induce the activity of ornithine decarboxylase (ODC), the first and rate-limiting enzyme for polyamine biosynthesis, in their target tissues. Using ovariectomized rats, we have compared the effects of sex hormones on ODC activity in the uterus and the kidney which contain estrogen and androgen receptors. The results show that 1) both estrogen and androgen stimulate renal ODC activity, 2) estrogen but not androgen effectively increases ODC activity in the uterus, 3) estrogen at higher dosage can stimulate renal ODC activity to an extent similar to that in the uterus, 4) daily treatment with estradiol for 5 days results in the desensitization of uterine ODC activity, but not that of renal ODC activity to the hormonal stimuli. Although both uterus and kidney are targets of sex hormones, our results indicate that estrogen and androgen have differential influences on the ODC activity in these two organs.