ENZYME-LINKED-IMMUNOSORBENT-ASSAY FOR THE DETECTION OF TOTAL CATHEPSIN-H IN HUMAN TISSUE CYTOSOLS AND SERA

An enzyme-linked immunosorbent assay (ELISA) was constructed for the d etermination of total human cathepsin H concentration in clinical samp les. Utilising monoclonal and polyclonal antibodies, raised to human l iver cathepsin H, the assay is able to detect a mature protein, a prec ursor molecule and enzyme-inhibitor complexes. The test system permits sensitive and reliable detection of analyte either in tissue cytosols or in sera. The detection limit is 2 ng/ml (n = 10, mean of zero stan dard +/- 3 SD). The average recovery of cathepsin H, added to the low content samples, was 95.3% +/- 1.8%. The within-run and between-run co efficient of variance (CV) varied from 2.3% to 8.9% and 12.7% to 16.4% , respectively, indicating satisfactory reproducibility of the method. The level of cathepsin H was defined in tissue cytosols of human hear t, muscle and kidney and in sera from 30 healthy individuals. Addition ally, cathepsin H was measured in sera from 55 patients with primary s kin melanoma and from 42 patients with metastatic melanoma. The mean c athepsin H level was significantly higher for both groups of patients compared to normal sera level, being highest for metastatic melanoma p atients.