Development of a rapid and sensitive immunofluorometric assay for glutathione S-transferase A

Abstract

Background: The short half-life of the α-class glutathione S-transferases (GSTAs) in plasma combined with their even distribution throughout the liver lobule suggests that they may be useful complements to the more traditionally used liver markers. However, the currently available assays for measuring GSTAs in biological fluids have a poor dynamic range and are cumbersome, requiring multiple steps and prolonged incubation times. Methods: Hybridomas that secrete monoclonal antibodies to human GSTAs were produced and used to develop a rapid one-step immunometric assay for the determination of GSTA in serum. The assay uses a time-resolved immunofluorometric assay (TR-IFMA) format and requires 35 min of incubation. The reference interval was determined using 208 serum samples from healthy blood donors. We also compared our TR-IFMA with a commercially available enzyme immunoassay (EIA) for GSTAs. Results: The assay had a detection limit of 0.07 μg/L with a measuring range up to 625 μg/L. Within-run imprecision (CV) was 1.8-2.6% over the concentrations of GSTA tested (2.5-311 μg/L), with a between-run CV of < 5%. In healthy blood donors, the median values and reference intervals were 2.0 μg/L and 0.6-7.2 μg/L for females and 2.6 μg/L and 0.7-9.8 μg/L for males, respectively. GSTA concentrations determined with the TRIFMA correlated well with those obtained using a commercially available EIA. Conclusions: This report describes a new assay for monitoring the concentrations of GSTAs in human serum. The method may be useful in further evaluating the potential of monitoring serum GSTAs in the routine clinical setting. © 2001 American Association for Clinical Chemistry.