Objectives: To investigate whether angiotensin II has a role in the regulation of bladder smooth muscle growth and function, we developed a model of bladder neck obstruction (BNO) in the neonatal rabbit and investigated the effect of captopril (angiotensin converting enzyme inhibitor) on the obstructive changes in the developing bladder.
Methods: Partial BNO was induced in a group of 2-day-old rabbits (n = 8) by placing a loose 2-0 silk ligature around the vesicourethral junction. A second group of rabbits subjected to the identical partial BNO procedure (n = 8) was given captopril (1 mg/kg/day). Twelve days postobstruction, bladders from these animals, along with paired controls (n = 8), were harvested and assayed for total protein, DNA, and collagen content.
Results: Partial BNO resulted in a 170% increase in wet weight (P < 0.05), 132% increase in protein/deoxyribonucleic acid (DNA) ratio (P < 0.05), 75% increase in total DNA (P < 0.05), and 115% increase in total collagen (P < 0.05). When compared with obstructed animals, captopril administration significantly inhibited the increase in total DNA (P < 0.05) and reduced the amount of total collagen (P = 0.054). Examination of histology specimens demonstrated that captopril inhibited the serosal hyperplasia and collagen deposition associated with obstruction.
Conclusions: These data demonstrate that captopril partially inhibits the changes in the neonatal rabbit bladder associated with obstruction, supporting the hypothesis that angiotensin II is involved in the regulation of bladder smooth muscle growth and collagen production.