Portal hypertension is accompanied by hyperdynamic systemic and splanchnic circulation. Serum bile acids (BAs), which are elevated in portal hypertension and have vasodilatory properties, have been proposed as mediators of this hyperdynamic circulation. In this study, portal hypertensive rats [accomplished by partial portal vein ligation (PVL)] were gavaged with cholestyramine (PVL-CH) to decrease circulating BA levels. A control group of rats was gavaged with an inert suspension of Metamucil (PVL-ME). The following hyperdynamic parameters were found to be similar in PVL-CH and PVL-ME: mean arterial pressure (119 +/- 6 vs. 124 +/- 5 mmHg), portal pressure (13.2 +/- 0.6 vs. 14.5 +/- 0.5 mmHg), cardiac index (0.33 +/- 0.04 vs. 0.34 +/- 0.03 ml.min-1.g body wt-1), splanchnic blood flow (1.4 +/- 0.13 vs. 1.6 +/- 0.1 ml.min-1.g body wt-1), portosystemic shunting (82 +/- 8 vs. 92 +/- 3%), peripheral arteriolar resistances (344 +/- 74 vs. 387 +/- 29 mmHg.min.ml-1.g body wt), and splanchnic arteriolar resistances (75 +/- 14 vs. 72 +/- 6 mmHg.min.ml-1.g splanchnic wt; 1,471 +/- 150 vs. 1,325 +/- 120 mmHg.min.ml-1.g body wt). BA in PVL-ME (84 +/- 9 microM/l) were similar to those previously observed in untreated PVL and significantly greater than those measured in PVL-CH (25 +/- 4 microM/l; P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)