Intraoperative evaluation of big-endothelin plasma levels during liver transplantation in different vascular compartments

Gadolinium chloride-induced improvement of postischemic hepatic perfusion after warm ischemia is associated with reduced hepatic endothelin secretion

Selective Kupffer cell blockade by gadolinium chloride (GdCl(3)) pretreatment of liver donors previously proved to be effective in reducing ischemia/reperfusion injury in rat liver transplants. Physiological mechanisms of this effect have not been specified so far. Vasoactive peptides are involved in liver blood flow regulation. We tested the hypothesis, that hepatic hemodynamic effects of GdCl(3) pretreatment are mediated by intrahepatic endothelin-1 (ET) secretion in a standardized porcine model of warm liver ischemia and reperfusion. Standardized warm hepatic ischemia (45 min) was induced after laparotomy in intubation narcoses (ITN) by Pringle-maneuver in pigs (n = 12). Animals were either pretreated with GdCl(3) (20 mg/kg i.v.) or sodium chloride 0.9% (control group) in a randomized manner 24 h before investigation. Relaparotomy was performed at day 7. Before, during ischemia and until 6 h after liver reperfusion, transhepatic blood flow (portal venous + hepatic artery flow) was defined by ultrasonic flow probes and hepatic parenchymous microcirculation evaluated by implanted thermodiffusion electrodes. ET plasma concentrations were analyzed (commercial RIA) at all time points in the hepatic veins after selective canulation. GdCl(3) pretreatment of animals markedly improved hepatic macro- and microperfusion before and particularly after warm ischemia. Mean ET plasma concentrations in the hepatic vein were significantly lower before, 6 h and 7 days after ischemia, compared with controls. Kupffer cell destruction by GdCl(3) pretreatment improves hepatic micro- and macroperfusion after warm ischemia, thus indicating reduced ischemia/reperfusion injury. Documented reduction of postischemic liver blood flow impairment after GdCl(3) pretreatment could be mediated by a decreased hepatic ET secretion, as hemodynamic effects were associated with significantly reduced ET plasma levels in hepatic veins.

Effects of exogenous endothelin-1 application on liver perfusion in native and transplanted porcine livers

PURPOSE

This study was designed to assess and differentiate the impact of progressivly increasing portal venous endothelin-1 (ET) plasma concentrations on hepatic micro- and macroperfusion of native porcine livers (Group A) and liver grafts after experimental transplantation (Group B).

METHODS

A standardized gradual increment in systemic ET plasma concentration (0-58 pg/ml) was induced by continuous ET-1 infusion into the portal vein in both groups (A: n = 10, B: n = 10). Control animals received only saline (n = 5, each group). Hepatic microcirculation (HMC) was quantified by thermodiffusion electrodes, hepatic artery flow (HAF), and portal venous flow (PVF) by Doppler flowmetry.

RESULTS

No changes in ET or perfusion parameters were observed in controls. The mean ET level after orthotopic liver transplantation (OLT) in Group B was elevated (baseline: 3.8 +/- 2.4 pg/ml) compared with Group A (2.8 +/- 1.9 pg/ml). With rising ET levels HAF decreased progressively in Group A from 205 +/- 97 (baseline) to 160 +/- 72 ml/min, and in Group B from 161 +/- 87 to 146 +/- 68 ml/min. PVF decreased in Group A from 722 +/- 253 to 370 +/- 198 ml/min, and in Group B from 846 +/- 263 to 417 +/- 203 ml/min. Baseline HMC in Group A was 86 +/- 15 and decreased significantly to 29 +/- 9 ml/100 g/min, and baseline MC in Group B was 90 +/- 22 and decreased to 44 +/- 32 ml/100 g/min. No significant alteration in systemic circulation was noted at the ET concentrations investigated.

CONCLUSIONS

Significant impairment of hepatic micro- and macrocirculation was detected after induction of systemic ET levels above 9.4 pg/ml both in native and in transplanted livers. Disturbance of HMC was caused predominantly by reduction of portal venous flow, while the effect of ET on HAF was less pronounced. Characteristics of flow impairment in transplanted and native livers were analogous after short cold ischemic graft storage (6 h).

Validation of endothelin (ET) immunoreactivity in human bile by HPLC. Comparison of biliary ET concentration in liver transplant recipients with values obtained during cholecystectomy

High endothelin (ET) concentrations were recently detected in human bile after orthotopic liver transplantation (OLT). In the present study we compared biliary ET/big-ET levels measured by radioimmunoassay (RIA) in liver graft recipients (n = 37) with levels measured in non-transplant patients during cholecystectomy (n = 38) to clarify the influence of transplantation on the levels of biliary ET peptides. HPLC elution profiles of biliary ET were analyzed for characterization of ET peptide composition and validation of RIA analysis in bile extracts. Mean ET/big-ET levels in the common bile duct after OLT were significantly elevated (ET, 20.9 +/- 15; big-ET, 39.2 +/- 19 fmol/ml) compared to levels in non-transplant patients (ET, 5.7 +/- 4.9; big-ET, 12 +/- 8 fmol/ml). Highest ET/big-ET levels were measured in the gall bladder during cholecystectomy (ET, 61.7 +/- 41; big-ET, 75 +/- 28 fmol/ml). ET and big-ET levels were correlated by linear regression. HPLC analysis reveals the presence of high levels of ET/big-ET in human bile. Biliary ET mostly represents ET-1. High biliary ET levels after OLT appear to be derived from active endothelial secretion and probably reflect hepatic endothelial stress after preservation/ reperfusion. High biliary ET levels could be involved in the mediation of functional cholestatic syndromes after OLT.