In the course of studies of reabsorption by the kidney tubule, it was noted that phlorizin and glucose change the rate of reabsorption of AcAc, SO 4 and PO 4 . Phlorizin raises, while glucose depresses, the Tm for each of these ions. The effects of glucose and phlorizin on AcAc reabsorption were small, difficult to produce, and showed a tendency to recover. In contrast, the effects on SO 4 and PO 4 reabsorption were marked, easy to produce and showed no tendency to recover. It was thought that the molar rates of reabsorption might be determinants, and this in turn might be a measure of their relative affinities for a common reabsorptive path. A study of the interrelations of the three anions during maximal rates of reabsorption revealed that no such simple relationship exists. In an attempt to separate further the three transport mechanisms, the effect of the anions, NO 3 and SCN on Tmacac, Tmso 4 and Tmpo 4 were studied and again no consistent reabsorptive pattern was discovered. The data point to net transport mechanisms which are in part shared and in part separate for each of the three anions.
Cohen et al. (1957) studied this question.