A useful ELISA system for human liver-type arginase, and its utility in diagnosis of liver diseases

Objectives: To develop a new ELISA system for liver-type arginase using mon oclonal antibodies against the enzyme, and to verify the utility of the arg inase in diagnosis of hepatic disorders. Design and Methods: We have developed an enzyme-linked immunosorbent assay (ELISA), using two kinds of monoclonal antibodies (Mo6G3 and Mo9C5) for hum an liver-type arginase as the first and second antibodies respectively. We have also developed a new method to eliminate the influence of erythrocyte- derived arginase contamination in hemolytic samples. This ELISA was applied to specimens received from patients with acute and chronic hepatic disease and also patients who had undergone partial hepatectomy. Results: This assay is sensitive and reproducible for the measurement of li ver-type arginase in the sera of patients with liver dysfunction, and enabl ed us to detect enzyme concentrations as low as 27 pmol/L without any proce ssing of the samples. The assay showed with-in-run coefficients of variatio n (CV) ranging from 1.9 to 4.1% and between-day CV from 3.6 to 5.1% for arg inase concentrations varing from 57.1 to 1200 pmol/L. The recovery was 113% (mean) with a range of 96 to 129%. These antibodies reacted strongly with both recombinant and native liver-type arginases, while, to some extent, wi th erythrocyte-derived arginase. Correction for erythrocyte-derived arginas e contamination in hemolytic samples was, however, easily made by assaying peroxidase-like activity of hemoglobin. From the view of a limited localiza tion of arginase in the liver, the marked increase of the enzyme in serum r eflects initiation of liver injury, while the rapid decrease reflects termi nation of the damage. Such quick normalization in circulating liver-type ar ginase indicated another merit of the enzyme in diagnosis of liver diseases . Conclusions: The changes in circulating liver-type arginase level could be helpful not only in the diagnosis of liver diseases but also subsequent tre atment of the patients with liver damage. (C) 2001 The Canadian Society of Clinical Chemists. All rights reserved.