Intrinsic urethral closure mechanisms in the female pig.

This study investigates the role of the various components of the female pig urethral wall in the generation of the urethral closure pressure. Prior to voiding urethral pressure fails and this is accompanied by a rise in lamina propria blood flow. Pharmacological manipulation shows that striated muscle is not involved in the generation of the urethral closure pressure. Drugs active upon smooth muscle change urethral pressure significantly by a mechanism independent of their cardiovascular system effects. Histological studies show that it is possible to correlate the disposition of circular smooth muscle with the urethral pressure profile. In vitro smooth muscle from the high pressure zone is pharmacologically different to that from the proximal urethra in a manner which may reflect their physiological roles.