Renal Tubular Uptake of Protein: Effect of pH

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Abstract
The present study was performed to determine to what extent pH influences protein reabsorption in renal proximal tubule cells. Rat surface proximal tubules were microinfused in vivo with 125I-labelled albumin in buffer solutions at different pHs. Tubular uptake was determined as the difference between microinfused and urinary trichloroacetic acid-precipitable radioactivity. In separate experiments the tubular uptake was followed by electron microscope autoradiography. The results showed that the uptake at pH 4.5 and 6.0 was about 15% higher as compared to uptake at pH 7.4. Furthermore, the electron microscope autoradiography demonstrated that albumin is taken up by endocytosis at acid pH as under normal conditions.