Erectile dysfunction is common in men with chronic renal failure. Previously nitrergic and endothelium-dependent relaxation responses have been shown to be reduced in chronic renal failure rabbits. We have therefore investigated the efficacy of phosphodiesterase inhibitors on the corpora cavernosa obtained from uremic rabbits. Uremia was induced with 5/6 nephrectomy and 4 weeks later cavernosal tissue strips were isolated. The relaxant effect of phosphodiesterase 5 inhibitors, zaprinast (1 -300 muM) and sildenafil (0.01 -300 muM), phosphodiesterase 3 inhibitor amrinone (1 -100 muM) and non-specific phosphodiesterase inhibitor papaverine (1 - 300 muM) were investigated on phenylephrine (10 muM)-induced tone. We found a shift in the dose-response curve of only phosphodiesterase 5 inhibitors. These results suggest that the decreased production or availability of endogenous nitric oxide in chronic renal failure animals leads to decreased efficacy of phosphodiesterase 5 inhibitors to induce relaxation. (C) 2003 Elsevier Science B.V. All rights reserved.