Turnover and tissue uptake of rabbit ferritin from rabbit plasma

Using a two-site immunoradiometric assay for rabbit liver ferritin normal NZW rabbits were found to have very low plasma ferritin concentrations (less than 4 micrograms/l). Purified preparations of rabbit liver and kidney ferritin were labelled with 125I and injected into rabbits. Clearance from plasma was extremely rapid with an initial half-life of 1-2 min as measured by immunoprecipitation of labelled ferritin. The rate of clearance was unaffected by the labelling procedure and by the method of ferritin purification. Autoradiography and organ uptake studies showed that 125I-rabbit liver ferritin was removed mainly by liver reticuloendothelial cells, although on a weight basis, spleen had the greatest radioactivity. These studies indicate that rabbit ferritin released into the circulation is promptly cleared by the RES.