Progressive hyperplastic lesions of the bladder uroepithelium after hormone stimulation in Nb rats.

The bladder epithelium of female Nb rats was markedly stimulated by treatment with pellets of testosterone propionate. Estrone treatment simultaneously reduced the incidence of bladder changes to approximately 50 per cent although estrone alone had no effect on bladder weights. The bladders of male rats were less responsive to hormones and were stimulated only by treatment with estrogen + testosterone. Massive papillary hyperplasia of the uroepithelium that extended into the kidney pelvis could be produced by hormones in the absence of calculi. Transplants of hyperplastic bladder epithelium usually resulted in small pseudo-bladders, but in one case a transplantable squamous cell carcinoma developed.