Quantitation of functional differences between the two segments of the rat proximal tubule in the handling of chlorphenol red and hippuran-131I.

Abstract

The work reported in this paper attempts to associate several functions known to occur in the renal proximal tubule with either the convoluted or straight segment of this tubule, and from observations made on a zonal basis to offer conclusions concerning the specific functions of these segments. Measurements were made of chlorphenol red and hippuran‐131I in kidneys of diuretic rats which had one ureter ligated to create stop‐flow conditions. Autoradiographs were also obtained from the hippuran‐131I study.The results show that chlorphenol red and hippuran‐131I accumulate in the cortex in kidneys after ligation of the ureter and in the outer stripe of the outer zone of medulla in free urine flow kidneys.The measurements made in renal tissue when compared with the plasma and urine levels of chlorphenol red and hippuran‐131I obtained during the experiments, indicate that these substances are actively secreted at both the vascular and luminal margins of the epithelial cell of the convoluted segment and passively reabsorbed by the epithelial cells of the straight segment.