Eosinophil peroxidase and 125I- ion binding in guinea-pig trachea.

The present study further characterizes ascorbic acid-dependent 125I- ion binding in guinea-pig trachea. Binding of 125I- ion in the presence of ascorbic acid was detected at the epithelial/submucosal interface, apparently involving individual cells containing peroxidase enzyme. A similar binding pattern was observed when hydrogen peroxide was substituted for ascorbic acid. Binding could be inhibited by the addition of the H2O2 degrading enzyme catalase or the peroxidase inhibitor thiourea. Results demonstrated that this binding was dependent upon the addition of, or endogenous production of hydrogen peroxide and its metabolism via airway eosinophil peroxidase. The relevance of this anomalous iodine binding phenomenon to radioiodinated ligand binding studies is discussed.