Decreased vascular reactivity of portal vein in rats with portal hypertension

Background/Aims: Vascular hyporesponsiveness in portal hypertension is well documented in the arterial tissue. The present study aimed to investigate the possible changes in the portal vein from portal hypertensive rats. Methods: Portal hypertension was induced by partial portal vein ligation. Fourteen days after surgery, portal veins were removed for contractile study and measurement of cAMP, cGMP and [Ca2+](i). Results: In vitro tension preparation showed a decreased maximum response to norepinephrine in portal vein of portal vein ligated rats (38.3+/-4.1 vs, 23.4+/-1.5 mN/mm(2)). The pA(2) values of WB4101 and yohimbine (alpha(1)- and alpha(2)-adrenoceptor antagonist, respectively) were not different between the two groups. Tissue cAMP (14.4+/-0.9 vs, 12.2+/-0.7 pmol/mg protein), but not cGMP, content was increased and intracellular calcium [Ca2+](i) levels (247+/-9 vs. 281+/-13 nM) were decreased in portal vein ligated rats. Conclusions: These results showed that in portal vein from portal vein ligated rats, vascular hyporesponsiveness and an increase in basal cAMP content and a decrease in basal [Ca2+](i) were observed.