Liver-type arginase in serum during and after liver transplantation: a novel index in monitoring conditions of the liver graft and its clinical significance.

We quantified liver-type arginase in sera of 47 patients undergoing partial liver transplantation with use of an ELISA method. The level of liver-type arginase fluctuated slightly beyond the normal range in successful liver recipients, while it changed more drastically or precipitously in unsuccessful ones, accompanying or unaccompanying elevation of AST and ALT levels. A higher elevation pattern of the arginase level (above 100 ng ml-1) was observed in each of the unsuccessful recipients with critical condition, except for one patient. Other hepatic markers (LDH, ALP, and T-BIL) remained relatively unchanged until the terminal stage of deceasing patients. The finding that the liver-type arginase emerged in large quantity in the blood stream immediately after reperfusion of the liver graft indicates that the enzyme leaks out of hepatocytes damaged, presumably, by storage in the absence of circulation. A half-life of the liver-type arginase in the human blood was estimated to be 1 h, that is clearly shorter than that of AST. The short half-life of the arginase appears to be ascribable, at least partly, to formation of an immune complex with circulating autoantibody which appears in many liver recipients. These results suggest that liver-type arginase behaves uniquely in the serum among many hepatic enzymes, and could serve as a distinct marker of hepatic lesions, particularly during and after liver transplantation.