This study in the anaesthetized rabbit aimed at determining the role of nitric oxide (NO), the putative endothelium-derived relaxing factor, in the regulation of haemodynamics and the release into plasma of noradrenaline and adrenaline. Specific inhibition of NO formation was achieved by i.v. bolus injection of L-NG-monomethyl-arginine (L-NMMA; 3-100 mg kg-1). Phenylephrine was infused i.v. at constant rates (2.5-20 micrograms kg-1 min-1) in order to assess baroreflex-mediated changes in release due to direct peripheral vasoconstriction. Rates of noradrenaline and adrenaline release into plasma were determined by the radio-tracer technique. L-NMMA, but not D-NMMA, dose-dependently increased mean arterial pressure and total peripheral vascular resistance, whereas both heart rate and cardiac output decreased concomitantly. The corresponding ED50 values for L-NMMA ranged from 11.2 to 18.5 mg kg-1. Inhibition of NO formation by L-NMMA as well as phenylephrine infusion caused decreases in the plasma clearance of noradrenaline and adrenaline which were correlated with the drug-induced decreases in cardiac output. Both L-NMMA and phenylephrine reduced the rate of noradrenaline release into plasma as they increased total peripheral resistance. Moreover, the curvilinear relationship between these two parameters obtained for L-NMMA was virtually identical to that produced by phenylephrine, indicating that the reduction in noradrenaline release by L-NMMA is mediated solely by the baroreflex. From the L-NMMA-induced maximum inhibition of noradrenaline release, it is concluded that the counter-regulation against peripheral vasodilation by NO accounts for 69% of basal noradrenaline release.(ABSTRACT TRUNCATED AT 250 WORDS)

Our study was aimed at developing a reliable method of hyperthermic isolated liver perfusion (HILP) in pigs and at assessing its local and systemic side effects. HILP was performed via the hepatic artery and portal vein in 15 animals. The perfusate consisted of blood (200 ml), oxypolygelatine (500 ml), Ringer's solution (1000 ml), and trapped intrahepatic blood. HILP was carried out for 45 min at a mean perfusate inflow temperature of 41.2 degrees C. The mean portal flow and pressure were adjusted to 500 ml/min and 20-25 mm Hg; the mean arterial flow and pressure were 130 ml/min and 40-60 mm Hg, respectively. After 20 min of perfusion the mean temperature in the right and the left liver lobe were 40.8 degrees C and 40.3 degrees C and remained almost constant over the whole perfusion period. Liver enzymes (alanine aminotransferase and aspartate aminotransferase) and serum lactate levels showed slight increases after perfusion but normalized within 1 week. Histology of liver parenchyma showed only mild pathological changes, which were also reversible within 7 days. The presented method of HILP is a safe and reproducible technique for isolated hyperthermic liver perfusion. Based on this animal model, experimental HILP with different chemotherapeutic agents can be investigated in order to assess hepatic and systemic toxicity of this therapy.

Summary. In the anaesthetized rabbit, L-NG-monomethyl-arginine (L-NMMA) , a specific inhibitor of nitric oxide (NO) formation, was used to assess the role of endothelium-derived NO in the regulation of haemodynamics and noradrenaline release (RNA). L-NMMA dose-dependently increased mean arterial pressure and total peripheral resistance (TPR) , but decreased heart rate, cardiac output and RNA. The curvilinear relationship between RNA and TPR obtained for L-NMMA was virtually identical with that produced by phenylephrine, indicating that L-NMMA-induced decreases in RNA are mediated by the baroreflex. Since the maximum RNA inhibition by L-NMMA was 69%, the counterregulation against peripheral vasodilatation by endothelium-derived NO accounts for 69% of basal RNA.

Isolated hyperthermic perfusion of the liver was performed for 45 min in 27 pigs via hepatic artery and portal vein at mean inflow temperatures between 40.7 and 41.2°C. In two study groups B and C (n = 9 pigs each) 50 μg recombinant human tumor necrosis factor-α (rhTNFα) per kg body weight were added to the perfusate, whereas in a control group A liver perfusion was done without rhTNFα. Before reperfusion the livers were washed out with Ringer’s solution in all groups followed by a protein solution in group C. At 30 and 60 min after reperfusion the maximum systemic rhTNFα concentrations were significantly higher in group B with 68 and 61 ng/ml compared to 14.5 and 14.9 ng/ml in group C (p < 0.05). Mean systemic porcine TNFα concentration was significantly higher in group B (217 pg/ml) compared to group C (50 pg/ml) 30 min after reperfusion (p = 0.012). Survival was 7/9 in group A and C and only 2/9 in group B with 6/7 pigs dying due to severe cardiopulmonary failure within 12 h after operation. In surviving pigs of group A and C only mild and transient hepatotoxicity was registered. The presented study underlines the feasibility of high dose rhTNFα application in an isolated hyperthermic liver perfusion system. Washout of the liver with a protein solution before reperfusion reduces systemic TNFα levels as well as associated lethal cardiocirculatory and hepatotoxic side effects.