Na restriction blunts expansion of plasma volume and ameliorates hyperdynamic circulation in portal hypertension.

Expansion of plasma volume may be necessary for the development of the hyperdynamic circulation in portal hypertension. In experiment 1, sham portal vein-constricted (sham PVL) rats were divided into normal diet (NL diet sham) and low-sodium diet (low-Na sham) groups. Data obtained from the NL diet sham group was used as control data in studying portal hypertensive rats, which were also divided into normal diet (NL diet PVL) and sodium-restricted (low-Na PVL) groups on the day of portal vein constriction. There were no hemodynamic differences at 3 wk between sham PVL rats on the two diets. In contrast, sodium restriction in PVL rats resulted in a significant amelioration of the hyperdynamic circulation. In experiment 2, PVL rats were fed a normal diet for 10 days, followed by allocation to NL diet PVL and low-Na PVL groups. The hemodynamic effects of sodium restriction in these animals (studied at 22 and 28 days after PVL) were similar to those observed in experiment 1. A time course for amelioration of the hyperdynamic circulation in PVL rats by sodium restriction is described. Sodium restriction prevents the expansion of the plasma volume in PVL rats. Interference with plasma volume expansion blunts the development of (and can ameliorate) the hyperdynamic syndrome. Plasma volume expansion seems necessary for the development of the hyperdynamic circulation in portal hypertension.