Background/aims: The venous system is the primary capacitance region in the body. However, the influence of active changes in the venous system on the hemodynamic alterations of portal hypertension is poorly understood. To investigate venous compliance (VC) in conscious partial portal vein ligated rats (PPVL) and the effect of propranolol on VC.
Methods: Venous compliance was derived from the relationship between changes in mean circulatory filling pressure (MCFP) and changes in blood volume (BV). Measurements were performed before and after i.v. propranolol (7.5 mg/Kg) or placebo in rats with portal hypertension due to PPVL and sham operated controls.
Results: PPVL rats had an increased VC when compared to Sham (4.9+/-1.4 vs. 3.7+/-0.9 ml kg-1 mm Hg-1; P<0.02). VC did not change after placebo but was significantly reduced by Propranolol in PPVL (-32.9+/-15.7%; P<0,007). Propranolol did not modify venous compliance in sham operated rats (+10.9+/-13.4%; P=ns).
Conclusions: Venous compliance is increased in portal hypertensive rats, suggesting that the venous system contributes to the profound circulatory changes encountered in portal hypertension. The increased venous compliance is markedly attenuated by propranolol, suggesting that this abnormality is related to increased adrenergic activity.