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

Background: The short half-life of the a-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 traditiona lly used liver markers. However, the currently available assays for measuri ng 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 de termination of GSTA in serum. The assay uses a time-resolved immunofluorome tric assay (TR-IFMA) format and requires 35 min of incubation. The referenc e interval was determined using 288 serum samples from healthy blood donors . We also compared our TR-IFMA with a commercially available enzyme immunoa ssay (EIA) for GSTAs. Results: The assay had a detection limit of 0.07 mug/L with a measuring ran ge up to 625 mug/L. Within-run imprecision (CV) was 1.8-2.6% over the conce ntrations of GSTA tested (2.5-311 mug/L), with a between-run CV of <5%. In healthy blood donors, the median values and reference intervals were 2.0 mu g/L and 0.6-7.2 mug/L for females and 2.6 mug/L and 0.7-9.8 mug/L for males , respectively. GSTA. concentrations determined with the TR-IFMA correlated well with those obtained using a commercially available EIA. Conclusions: This report describes a new assay for monitoring the concentra tions of GSTAs in human serum. The method may be useful in further evaluati ng the potential of monitoring serum GSTAs in the routine clinical setting. (C) 2001 American Association for Clinical Chemistry.