PHYSIOLOGICAL-ROLE OF NITRIC-OXIDE IN GALLBLADDER EMPTYING IN MEN

This study was designed to determine the role of nitric oxide in gallb ladder (GB) contractions in men. The studies were performed in 10 youn g healthy male volunteers, GB emptying was examined by ultrasonography under basal conditions and after intravenous infusion of cholecystoki nin (CCK8; 12.5 pmol/kg.h) or yolk intake in tests without (saline) an d with intravenous infusion of N-G-monomethyl-L-arginine (L-NMMA; 4.0 mu mol/kg.h) and/or L-arginine (1 mmol/kg.h). The plasma CCK level was determined by radioimmunoassay. It was found that the basal GB volume was about 27 +/- 3 mi, and after CCK8 infusion or yolk meal this volu me was reduced within about 30 min by about 93 and 80%, respectively, Pretreatment with L-NMMA caused reduction of the baseline volume by ab out 15% and significantly augmented the GB emptying induced by CCK8 in fusion and yolk intake, L-Arginine alone failed to affect basal or sti mulated (CCK or yolk) emptying of the GB, but when combined with L-NMM A, it reversed the enhancement of GB contraction caused by L-NMMA. The basal plasma CCK level was 1.2 +/- 0.3 pmol/l and rose to 7.9 +/- 2.1 pmol/l with CCK8 infusion and to 4.7 +/- 1.8 pmol/l after yolk meal, No significant change in plasma CCK levels was observed in tests with L-NMMA and/or L-arginine. We conclude that under physiological conditi ons, the GB contractile activity is regulated predominantly by CCK, bu t endogenous nitric oxide has a tonic relaxing influence on this activ ity.