Effects of chronic treatment with vardenafil, a phosphodiesterase 5 inhibitor, on female rat bladder in a partial bladder outlet obstruction model

Abstract

To investigate whether vardenafil, a phosphodiesterase 5 (PDE-5) inhibitor, would protect the bladder from decompensatory changes in a 4-week rat bladder outlet obstruction (BOO) model, as evidence has been accumulating that PDE-5 inhibitors improve lower urinary tract symptoms (LUTS) in patients with benign prostatic hyperplasia (BPH). In all, 50 12-week-old female Sprague-Dawley rats were divided into five equal groups; group 1, sham operated vehicle control rats; group 2, BOO vehicle rats; group 3-5, BOO rats given oral vardenafil at 5, 20, 80 mg/L, respectively. Vardenafil was given in drinking water from the day of surgery. At 4-weeks after the introduction of BOO, vardenafil was washed-out by giving water for 24-48 h, and then the bladder was excised and dissected into four longitudinal strips for isometric organ-bath assay. Contractile responses of bladder strips to electrical field stimulation (EFS), carbachol and KCl was determined for each group. BOO induced a significant increase in bladder weight in group 2 compared with group 1. Bladder weights of groups 3-5 were not significantly different from that of group 2. The contractile forces in response to EFS, carbachol and KCl in group 2 were 30.7-51.7% of those in group 1. Vardenafil treatment in groups 3-5 generally did not block the BOO-induced reduction of contractile force in the bladder strips. However, treatment with a high dose of vardenafil resulted in a significant increase in the contractile response to carbachol (78.4% group 5 vs 51.7% group 2). Chronic treatment with a high dose of vardenafil protected the rat bladder from BOO-induced contractile dysfunction to carbachol.