Renal Tubular Reabsorption of Iodide as Compared with Chloride.

The hypothesis examined in this study is that iodide reabsorption is chiefly passives occurring in the same portions of the nephron as the reabsorption of chloride and other small monovalent anions, with the ratio of the permeability of the tubule to iodide to its permeability to chloride a constant. If this were true, iodide clearance and chloride clearance would be interrelated in a uniform manner, and it should be possible to predict iodide clearance from chloride clearance. Furthermore, the relationship between the two clearances should be independent of the plasma level of either halide. To test this hypothesis, observations have been made of simultaneous iodide and chloride clearances, varied over a wide range in individual experiments. Many different agents, singly and in combination, were employed to induce variations in halide clearance and plasma halide levels. In analyzing the results, it is desirable to use a simple mathematical model of the relationship between the two clearances and to ascertain whether this relationship is altered by the experimental manipulations. Such a model should have some theoretical support and should also give a good fit to the data. For passively reabsorbed solutes, a