Nitric oxide generation in a rat model of acute portal hypertension

Abstract Objective—To document blood nitric oxide concentrations in the portal vein and systemic circulation in a rat model of acute portal hypertension and compare values with a control group and a sham surgical group. Animals—30 rats; 10 controls (group 1), 10 sham surgical (group 2), and 10 rats with surgically induced acute portal hypertension (group 3). Procedure—Following induction of anesthesia, catheters were placed surgically in the carotid artery, jugular, and portal veins of group 2 and 3 rats and in the carotid artery and jugular vein of group 1 rats. Baseline heart and respiratory rates, rectal temperature, and vascular pressure measurements were obtained, and blood was drawn from all catheters for baseline nitric oxide (NO) concentrations. Acute portal hypertension was induced in the group 3 rats by tying a partially occluding suture around the portal vein and a 22-gauge catheter. The catheter was then removed, resulting in a repeatable degree of portal vein impingement. After catheter placement, all variables were remeasured at 15-minute intervals for 3 hours. Results—Blood nitric oxide concentrations were greater in all vessels tested in group 3 than in group 2 rats. Conclusions and Clinical Relevance—Acute portal hypertension in this experimental model results in increased concentrations of NO in the systemic and portal circulation. On the basis of information in the rat, it is possible that increased NO concentrations may develop in dogs following surgical treatment of congenital portosystemic shunts if acute life-threatening portal hypertension develops. Increased NO concentrations may contribute to the shock syndrome that develops in these dogs. (Am J Vet Res 2000;61:1173–1177)