Degradation of human 125I-interferon alpha by isolated perfused rabbit kidney and liver

Rabbit livers and kidneys were isolated and perfused with homologous blood. After equilibration, human IFN alpha labeled with 125I and an excess of cold IFN alpha were added, and blood samples were withdrawn at predetermined times. Protein-bound and acid-soluble radioactivity together with biological (antiviral) activity were measured. Our results show that although liver exerts a minimal catabolism, the kidney filters and breaks down a considerable amount of IFN alpha. The parallelism between protein-bound radioactivity and biological activity decay curves indicates that IFN carefully labeled with 125I can be reliably used for metabolic investigations.