Measurement of immunoreactive gamma-glutamyl transpeptidase in human sera and liver tissues of patients with various liver diseases.

Immunoreactive gamma-glutamyl transpeptidase in human serum and liver tissue was measured by a solid phase enzyme-linked immunosorbent assay. The immunoreactive gamma-glutamyl transpeptidase was significantly elevated in the sera of patient with hepatocellular carcinoma. On the other hand, in sera of patients with non-neoplastic diseases, including chronic hepatitis, acute hepatitis, fatty liver and hemangioma, the immunoreactive gamma-glutamyl transpeptidase was not elevated. In hepatocellular carcinoma and metastatic liver tumor tissues, the immunoreactive gamma-glutamyl transpeptidase content was also elevated, showing good correlation with the enzyme protein content in sera. However, no correlation was found between the activity of gamma-glutamyl transpeptidase determined by an enzymatic assay and the content determined by an enzyme-linked immunosorbent assay. On immunohistochemical examination, the immunoreactive enzyme protein without enzymatic activity was detected only in the cytoplasm of cancer cells. This suggested that there is an increased level of the immunologically active but enzymatically inactive form of gamma-glutamyl transpeptidase in hepatoma tissues.