MODULATION OF SMOOTH-MUSCLE ACTIVITY BY NITRIC-OXIDE IN THE HUMAN UPPER URINARY-TRACT

The aim of the study was to ascertain whether nitric oxide (NO) might regulate motility in the human upper urinary tract. Smooth muscle acti vity in the human renal pelvis and proximal ureter was studied in vitr o in organ baths, and nitric oxide synthase (NOS) activity was studied by measurement of citrulline formation. NO, glyceryl trinitrate (GTN) and sodium nitroprusside (SNP) significantly reduced the frequency of spontaneous rhythmic contractions in renal pelvis and proximal ureter . Exogenously applied NO elicited relaxations in pre-contracted renal pelvis. Calcium-dependent NOS activity was significant in the renal pe lvis but undetectable in the ureter. Also, NOS activity was absent in hydronephrotic renal pelvis. NO, SNP and GTN inhibited smooth muscle a ctivity in the human upper urinary tract. NOS activity was obtained in normal renal pelvis but not in hydronephrotic renal pelvis. Regulatio n of urinary tract NO concentrations might offer a strategy for treatm ent of renal colic and disturbances in upper urinary tract motility.