Transport of p-aminohippurate from cell to lumen in kidney tubule

Abstract

Intracellular accumulation of various anions in the rabbit kidney tubule has been well documented. The present experiments were designed to test the hypothesis that in the rabbit no further concentration step is required for the transfer of these materials from the cells into the tubular lumen. In such a case PAH should be accumulated in the cells to the same concentration as in the proximal tubular urine. The maximum active uptake in vivo was determined by measurement of intracellular PAH in kidney cortex rapidly removed from freshly killed animals with high plasma levels of PAH. A value of about 10 µmoles/ml cell water was obtained. The concentration of PAH in the tubular urine was estimated during massive osmotic diuresis on the assumption that bladder urine under these conditions approaches proximal tubular urine in composition. With simultaneous PAH and mannitol loading, a PAH concentration not exceeding 10 µmoles/ml proximal tubular urine was observed. The same value was calculated from results obtained by the stop-flow technique.