Correlation of Pulmonary Vascular Dilatation on HRCT to Expression of eNOS in a Rabbit Model of Hepatopulmonary Syndrome

ABSTRACT

PURPOSE: To investigate the correlation between pulmonary vascular dilatation on high-resolution computed tomography (HRCT) and expression of endothelial nitric oxide synthase (eNOS) after common bile duct ligation (CBDL) in the rabbit as a model of hepatopulmonary syndrome. MATERIALS AND METHODS: CBDL was done in 11 rabbits (2 weeks after CBDL, n = 5; 3 weeks after CBDL, n = 6). Four rabbits were done by abdominal incision with peritoneal suture only as a control group. HRCT scans were performed in the both groups. We evaluated peripheral pulmonary vascular dilatation in the upper and lower lobe. Tissue samples were immediately obtained from both upper and lower lobes of the lung and the liver after sacrifice. Dilatation of peripheral pulmonary vessel was correlated with the expression of endothelial nitric oxide synthase (eNOS) determined by Western blot. We also compared the degree of pulmonary vascular dilatation between the groups with administration of L-arginine (n = 5) and without administration of L-arginine (n = 6) after CBDL. RESULTS: Two weeks after CBDL, pulmonary vascular dilatation on HRCT was seen in three rabbits (60%) and the increase of eNOS expression was shown in two rabbits (40%) in the lower lobe. Three weeks after CBDL, pulmonary vascular dilatation on HRCT was seen in four rabbits (66.7%) and five rabbits (83.3%) each upper and lower lobe, respectively. Expression of eNOS was coincidently increased. The pulmonary vascular dilatation was noted more frequently in the lower lobe than in the upper lobe. Pulmonary vascular dilatation on HRCT was highly correlated with increase of expression of eNOS in the upper (r = 1.00, p = .0001) and lower lobe (r = .83, p = .0015). In contrast, control group of four rabbits developed neither pulmonary vascular dilatation on HRCT nor increase of eNOS expression. The grade of pulmonary vascular dilatation in the group with L-arginine administration was higher than that without administration of L-arginine (p < .05). CONCLUSION: Pulmonary vascular dilatation on HRCT is significantly correlated with increase of eNOS expression in a rabbit lung after CBDL. These results suggest that NO, derived from pulmonary eNOS, contributes to pulmonary vascular dilatation in a rabbit model of hepatopulmonary syndrome. Index words Lung, CT Lung, effect of drugs on Lung, vascular disease