| Abstract: | A case of hyperamylasemia with lung cancer is described. Macroamylasemia was excluded by a normal amylase/creatinine clearance ratio and by a sedimentation constant obtained by sucrose density gradient centrifugation. Positive immunofluorescent staining of tumor cells with a specific antibody against human salivary amylase and significant amylase activity in the primary tumor and metastases support the hypothesis of independent production of amylase by the lung tumor. Cellulose--acetate membrane electrophoresis demonstrated three bands of amylase activity. The major component corresponded to normal salivary amylase in electrophoretic mobility, isoelectric point and molecular size. The minor bands, one of which occupied about 10% of the total amylase activity in serum, urine and tissue homogenates, demonstrated a lower electrophoretic mobility and a more acidic isoelectric point. Gel filtration and electrophoresis disclosed that these minor bands were derived from an amylase isozyme with a larger molecular size than that of normal salivary amylase. The results suggest ectopic tumor production of heterogenous amylase isozymes, with the larger form being secreted into the circulation. |
