Enzyme-linked immunosorbent assay of human placenta type glutathione s-transferase and its application in the diagnosis of hepatocarcinoma

GST-π was purified from human placenta and its antiserum was raised in rabbits. The antibody IgG was purified and degraded into Fab’ fragment which was conjugated with horseradish peroxidase (HRP) using N-succinimidyl-4-(N-maleimido- methyl) cyclo-hexane-1-carboxylate (SMCC) as crosslinking reagent to produce Fab’-HRP conjugate. A sandwich ELISA was established for the microquantitative determination of GST-π. The sensitivity was 11 pg/tube, which was far more sensitive than the radioimmunoassay so far reported. Using this method, the serum GST-π of 41 cases normal adult was found to be 1.06±0.94 ng/ml. The upper limit of the normal value was 2.6 ng/ml. In 30 cases of primary hepatocarcinoma, the level, of serum GST-π was 24.4±17.4 ng/ml, which was 23 times higher than the normal average value (P<0.01). The positive rate was 90%. In contrast, serum GST-π in 25 cases of chronic hepatitis was determined to be 1.74±1.16 ng/ml, which was not significantly different from the normal value (P>0.05). The pseudo-positive rate was 12.0%.