NITRIC-OXIDE PRODUCTION IN ARTERIAL VESSELS OF CIRRHOTIC RATS

Indirect evidence exists implicating vascular nitric oxide in the path ogenesis of arterial vasodilation in cirrhosis. In the current study, a coincubation assay to estimate the vascular nitric oxide production was developed and the nitric oxide production by arterial segments of cirrhotic and control rats was assessed. In the assay, measurement of reporter monolayer cell-associated cGMP levels allows the influence of nitric oxide released by arterial segments to be determined. RFL-6 ce lls served as reporter cells. Nitric oxide production was determined i n thoracic aorta and mesenteric arteries of 22 control rats, 10 cirrho tic rats without ascites, and 12 cirrhotic rats with ascites. Basal an d bradykinin-stimulated (10(-6) mol/L) intracellular content of nitric oxide-dependent cGMP was significantly higher in RFL-6 cells coincuba ted with aortic segments of cirrhotic rats with (21.3 +/- 3.6 pmol/10( 5) cells, P < .05 and 44.7 +/- 7.0 pmol/10(5) cells, P < .025) and wit hout ascites (15.3 +/- 3.0 pmol/10(5) cells, P < .05 and 43.2 +/- 7.6 pmol/10(5) cells, P < .05) than in those incubated with aortic segment s of control rats (9.7 +/- 1.3 and 19.5 +/- 2.5 pmol/10(5) cells). RFL -6 cells exposed to bradykinin-stimulated mesenteric arterial segments of cirrhotic rats also showed increased cGMP content (ascitic: 2.73 /- 0.31 pmol/10(5) cells, P < .005; nonascitic: 2.58 +/- 0.51 pmol/10( 5) cells, P < .025) compared with cells exposed to control mesenteric arterial segments (1.28 +/- 0.15 pmol/10(5) cells). No differences bet ween cirrhotic and control vessels were observed after endothelium den udation. These results indicate that basal and bradykinin-stimulated v ascular nitric oxide production is higher in cirrhotic rats with and w ithout ascites than in control rats in and that the endothelial lining is the site where vascular L-arginine nitric oxide pathway activation takes place in experimental cirrhosis.