Nitric oxide synthase activity in the splanchnic vasculature of patients with cirrhosis: relationship with hemodynamic disturbances

Background/Aims: It has been demonstrated that an overproduction of nitric oxide plays an important role in the pathogenesis of the hyperdynamic circulation exhibited by cirrhotic patients. Nevertheless, evidence is supported by studies performed in experimental models or by indirect measurements in humans. The purpose of this study has been to evaluate nitric oxide production in splanchnic vasculature of patients with cirrhosis and to investigate its possible relationship with systemic and splanchnic hemodynamics. Methods: Nitric oxide synthase (NOS) activity was measured in hepatic artery and portal vein tissues of nine cirrhotic patients. Samples were obtained during liver transplantation. Control samples were obtained simultaneously from the corresponding tissues of the liver donors. Hemodynamic parameters were determined with Doppler ultrasonography. Results: NOS activity was significantly higher in hepatic artery of cirrhotic patients than in controls (8.17±1.30 vs 4.57±0.61 pmoles/g of tissue/min, P<0.05). Patients with ascites showed a higher hepatic artery NOS activity than patients without ascites. Highly significant correlation was observed between cardiac output and hepatic artery NOS activity as well as between portal blood flow and hepatic artery NOS activity. Conclusions: The present study demonstrates an enhanced production of nitric oxide in the splanchnic vasculature of patients with cirrhosis.