Distribution of iodide between cells and plasma as measured by means of radioactive iodide.

Scott, Reavis, Saunders, and White (1) have proposed a method of evaluating thyroidal function which depends upon knowledge of the distribution of iodide between erythrocytes and plasma in the blood. Their proposal is based upon the statement that the ratio C&/Cl, = 1,/I, = 0.5, where the subscripts c and p refer to cells and plasma, respectively. Earlier, Rall, Power, and Albert (2) had indicated that the iodide-131 ratio between cells and plasma was 14 per cent higher than the chloride ratio; i.e., 0.67 as compared with 0.59. Since other investigations also have suggested differences in cell-plasma distribution of the various halides (Table I), a further analysis of the problem was undertaken.