Decreased vascular reactivity of portal vein in rats with portal hypertension

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 nonrepinephrine in portal vein of portal vein ligated rats (38.3±4.1 vs. 23.4±1.5 mN/mm2). The pA2 values of WB4101 and yohimbine (a1- and a2-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.