Stimulation of Renal Deoxyribonucleic Acid Synthesis by a Pituitary-Derived Renotropin and Its Inhibition by Testosterone and Thyroxine*

Abstract

Kidney slices were obtained from castrated-hypophysectomized male rats treated with a single injection of several different gonadotropin preparations (2 ovine LH [luteinizing hormone] fractions, 1 bovine LH fraction, and 1 hCG [human chorionic gonadotropin] fraction) of vehicle, then incubated in a buffer containing [3H]thymidine. Only 1 of the above, an ovine LH preparation, increased [3H]thymidine incorporation into renal DNA, with a peak occurring 8-18 h after injection and; therefore; termed renotropin. In hypophysectomized rats with intact testes, such an effect was not observed. While testosterone propionate alone did not alter basal incorporaton in castrated-hypophysectomized rats, it abolished the incorporation that was stimulated by renotropin. Apparently, androgens, whether of testicular origin or exogenously administered, suppress the increased incorporation of [3H]thymidine stimulated by renotropin. This antagonistic effect of androgen was also observed with T4 [thyroxine], but to a lesser degree. The presence of renotropin, which could not be attributed to other known pituitary hormones was confirmed; there apparently is a complex interaction between this factor and 2 other renal growth-promoting hormones, testosterone and T4.