Ammonium-chloride-induced prostatic hypertrophy in vitro: urinary ammonia as a potential risk factor for benign prostatic hyperplasia.

To test the possibility that urinary ammonia could be a risk factor for benign prostatic hyperplasia (BPH), we explored the cellular effects of ammonium chloride (NH(4)Cl) on prostatic cancer cells used as an experimental model. Following treatment of human prostatic cancer DU-145 cells with the varying concentrations of NH(4)Cl for 3 days, cell growth was inhibited by approximately 50% at 5 mM NH(4)Cl and almost completely inhibited at 10 mM NH(4)Cl. However, the individual cell size in these treated cells became approximately 2-fold larger and cellular protein content was also up to 2.5-fold greater than in untreated cells. This protein increase appeared to result from the reduced protein degradation, verified by metabolic labeling with [(14)C]valine. Western blot analysis further suggested that such reduced protein turnover could in part be due to the inactivation of a lysosomal acid protease, cathepsin D. Taken together, these studies demonstrate NH(4)Cl-induced hypertrophy in prostatic cancer cells, as evidenced by the growth inhibition, cell enlargement, and cellular protein increase. Therefore, ammonia is not an inert metabolic product; instead, its chronic effects on the prostate may ultimately lead to significant cellular and biochemical alterations of the prostate such as BPH.