The effect of urine volume and nitric oxide on basal bladder blood flow: response to catheterization and drainage

Preliminary studies demonstrated that catheterization and drainage of the urinary bladder resulted in a significant increase in blood flow to the bladder. The objectives of this study were to determine 1) the relationship between urine volume and basal blood flow to the bladder smooth muscle and mucosa, 2) the effect of acute catheterization and drainage on bladder mucosal and smooth muscle blood flow, and 3) whether nitric oxide was involved in regulation of basal blood flow or the increase in blood flow observed after catheterization and bladder drainage. Twenty-four rabbits were separated into two groups: group 1 (14 rabbits) and group 2 (10 rabbits) treated with L-NAME (NOS inhibitor) 30 minutes before blood flow measurement. Blood flow was measured in all animals using a fluorescent microsphere technique before and immediately after catheterization and drainage of the bladder. The results demonstrated that 1) blood flow to the muscle and mucosa were independent of urine volume at the time of catheterization and drainage; 2) catheterization and drainage significantly increased blood flow to both the bladder smooth muscle and bladder mucosa, but not to the kidney; 3) L-NAME significantly reduced basal blood flow to the kidney, but not to the bladder smooth muscle or mucosa; and 4) L-NAME completely prevented the catheterization- and drainage-induced increases in blood flow to the bladder body mucosa and muscle. This study demonstrates that basal blood flow to the bladder smooth muscle and mucosa during filling is independent of NO control; although bladder blood flow may be increased significantly by NO synthesis and release during bladder emptying, and thus may be an important regulator of blood flow during and immediately following micturition.