Stimulation of renal deoxyribonucleic acid synthesis by a pituitary-derived renotropin and its inhibition by testosterone and thyroxine.

Kidney slices were obtained from castrated-hypophysectomized male rats treated with a single injection of several different gonadotropin preparations (two ovine LH fractions, one bovine LH fraction, and one hCG fraction) or vehicle, then incubated in a buffer containing [3H]thymidine. Only one of the above, an ovine LH preparation, increased [3H]thymidine incorporation into renal DNA, with a peak occurring 8-10 h after injection and therefore termed renotropin. However, in hypophysectomized rats with intact testes, such an effect was not observed. Furthermore, while testosterone propionate alone did not alter basal incorporation in castrated-hypophysectomized rats, it abolished the incorporation that was stimulated by renotropin. These results suggest that 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, but to a lesser degree. Our findings confirm the presence of renotropin, which could not be attributed to other known pituitary hormones, and suggest that there is a complex interaction between this factor and two other renal growth-promoting hormones, testosterone and T4.