Pressure-flow relationship in swine ureter: effect of nitric oxide synthase inhibition by L-NAME.

ABSTRACT

INTRODUCTION: The purpose of this report is to elucidate the possible role of nitric oxide (NO) in modulating smooth muscle tone of swine ureteral wall and its hydraulic resistance to urinary flow. MATERIALS AND METHODS: We performed direct monitoring of perfusion pressure for different flows in isolated fresh swine ureter. Fluid used for perfusions was saline or L-NAME 200 mumol saline added, and relative pressure-flow relationships were obtained. RESULTS: The general shape of pressure-flow relationships indicates a decrease of ureteral hydraulic resistance with increasing flow. NO synthase inhibition by L-NAME caused a statistically significant increase of perfusion pressures for every tested flow, hence of ureteral hydraulic resistance. CONCLUSIONS: Our data show an effective role of NO in modulating ureteral flow resistance, and suggest possible pharmacological implications. A simple mathematical approach to define hydraulic ureteral flow resistance for low and high urinary flows is also suggested.