A comparative study of chemically and enzymatically radioiodinated transferrin

A study was made of the physiological properties of rabbit transferrin which had been radioiodinated by the iodine monochloride method or by use of insolubilized lactoperoxidase as catalyst. The in vivo turnover rates of the protein labelled by either method were found to be identical. Similarly, the rates of uptake of iron from transferrin or the uptake of the protein itself by rabbit reticulocytes was not affected by the method of iodination. Furthermore, the uptake of iron and transferrin was the same from solutions of labelled transferrin or from fresh plasma containing in vivo screened transferrin. It is concluded that the physiological behaviour of transferrin is not altered by radioiodination using either of the procedures used in this work.