Aminoguanidine corrects hyperdynamic circulation without ameliorating portal hypertension and portal hypertensive gastropathy in anesthetized portal hypertensive rats

Background/aims: Portal hypertension and hyperdynamic circulation (i.e. generalized vasodilation and increased cardiac output and regional organ blood flows) may play an important role in the development of portal hypertensive gastropathy. This study investigated the effect of chronic administration of aminoguanidine, a selective inducible nitric oxide synthase inhibitor, to portal hypertensive rats on hemodynamics and the development of portal hypertensive gastropathy. Methods: Partial portal vein-ligated or sham-operated rats were randomly assigned to receive either placebo (distilled water) or aminoguanidine (~ 100 mg/kg per day subcutaneously) for 2 days prior to and 14 days. Hemodynamic studies with a thermodilution technique and gastric morphometric analysis were performed at 14 days after the operation. Results: In rats given placebo, portal vein-ligated rats had a significantly lower mean arterial pressure and systemic vascular resistance associated with a significantly higher cardiac index and portal pressure than sham-operated rats (p < 0.05). In portal vein-ligated rats aminoguanidine induced a significant increase in mean arterial pressure and systemic vascular resistance accompanied by a significant decrease in cardiac index (p < 0.05) without changes in portal pressure (p > 0.05). Despite persistence of portal hypertension, the aminoguanidine-treated portal vein-ligated rats had similar mean arterial pressure, cardiac index, and systemic vascular resistance as seen in placebo-treated sham-operated rats. The mean cross-sectional area of gastric mucosal vessels was significantly higher in placebo-treated portal vein-ligated than in placebo-treated sham-operated rats (p < 0.05). Treatment with aminoguanidine did not induce changes in the mean cross-sectional area of gastric mucosal vessels in either portal vein-ligated or sham-operated rats (p > 0.05). Conclusions: The results show that in portal hypertensive rats long-term aminoguanidine therapy corrects the hyperdynamic circulation without inducing changes in portal pressure and ameliorating the development of portal hypertensive gastropathy. This study suggests that, instead of correcting hyperdynamic circulation, treatment of portal hypertensive gastropathy should be aimed at reducing portal pressure.