Restriction of drinking water abrogates splanchnic vasodilation and portal hypertension in portal vein-ligated rats.

Portal hypertension is associated with splanchnic vasodilation which is claimed responsible for the maintenance of chronically elevated portal pressure. Vasopressin analogues are used in the treatment of acute variceal bleeding, since they effectively reduce splanchnic blood flow and portal pressure. Dehydration stimulates the release of endogenous vasopressin release. Here we compared the effects of deprivation of drinking water for 18 h with those of vasopressin infusion on mesenteric hemodynamics in portal vein-ligated (PVL) and sham-operated (SHAM) rats. Blood flow in the superior mesenteric artery was measured with the ultrasonic transit time shift technique. Deprivation of drinking water had no hemodynamic effects in SHAM rats, but completely reversed the mesenteric hyperemia and portal hypertension in PVL rats to figures measured in SHAM rats, without altering blood pressure. Similarly, intravenous infusion of low doses of arginine vasopressin (1-10 pmol/min) selectively reduced mesenteric blood flow in PVL rats but had little effect in SHAM rats. These data suggest that control of water balance or aquaretic drugs might have beneficial effects on splanchnic hemodynamics and portal pressure in advanced liver disease, possibly by stimulating endogenous vasopressin release.