Development of specific radioimmunoassays for the measurement of human hepatic basic and N/A2b glutathione S-transferases

A number of studies have indicated that plasma glutathione S-transferase (GST) measurements by radioimmunoassay (RIA) are superior to aminotransferase measurements at assessing hepatocellular damage [1,2]. In human liver three distinct groups of GST exist [3-S] and we have recently reported a purification scheme for GST in which three fractions of GST designated basic, N/Al and N/A2 were isolated 111. The basic fractions of GST could be further purified into five forms (a-c) which all shared immunological identity [1,3] and the N/A2 fraction could be further split into a minor component N/A2a and a major fraction N/AZb. Immunological studies showed that N/A2b and basic GST were immunologically distinct [l]. The published methods for measuring basic GST by RIA appear less sensitive than the corresponding methods described for the RIA of N/A2b GST [1,2,6]. These different sensitivities could be due to assay conditions or may merely reflect the quality of the antisera. This paper reports a detailed investigation into the RIA of basic (6 and E) and N/AZb GST, and describes assays with sufficient sensitivity to allow their measurement in serum taken from normal subjects and from patients with liver damage.