Relationship between vascular reactivity in vitro and blood flows in rats with cirrhosis

In cirrhosis there is a hyperdynamic circulation, which occurs mainly in th e systemic and splanchnic regions. Using isolated-vessel models, previous s tudies have shown reduced aortic reactivity to vasoconstrictors in rats wit h cirrhosis. The aim of the present study was to evaluate and compare the v ascular responsiveness to phenylephrine in arterial rings and the blood flo ws from different regions in rats with cirrhosis and controls. Reactivity w as studied in isolated thoracic aortic, superior mesenteric arterial and ca rotid arterial rings from sham-operated and bile-duct-ligated rats by measu ring the cumulative concentration-dependent tension induced by phenylephrin e (10(-9)-10(-4) M). Blood flows were measured by the radioactive microsphe re method. In rats with cirrhosis, a significant hyporeactivity to phenylep hrine was observed in both the aorta and the superior mesenteric artery com pared with the corresponding arteries of normal rats. This hyporesponsivene ss was corrected by N-omega-nitro-L-arginine (0.1 mM). In contrast, carotid artery reactivity and the responses to N-omega-nitro-L-arginine were simil ar in the cirrhotic and control groups. In each case. cardiac output and me senteric arterial blood flow were significantly higher in cirrhotic than in normal rats. Cerebral blood flows were not significantly different between the two groups. In cirrhotic rats, arterial hyporeactivity may be a conseq uence of increased regional blood flow and increased production of nitric o xide.