Autoradiographic study of cellular transport of hippuran-125I in the rat nephron

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Abstract
A new method of freeze-dry autoradiography was devised for determining the intrarenal distribution of water soluble compounds. Diffusion is prevented by the absence of contact between tissue sections and water prior to developing of the autoradiograph. Hippuran-125I was shown to be concentrated within the cells of the proximal tubules of the rat during the 45 sec. following intravenous or intrarenal artery administration. Uptake of hippuran by the proximal tubule was not homogeneous and tended to be more pronounced in the juxtamedullary region of the kidney. Within the 1st min. after a rapid intravenous injection of hippuran the cell-to-blood concentration ratio was found to be 8.1:1, SE 4.5 by grain counting. No accumulation of Hippuran-125I was detected in the cells of distal tubules. Autoradiographs from kidneys removed more than 45 sec. after hippuran administration showed a rapid diminution in cellular radioactivity and the appearance of maximum hippuran concentration in the lumen of distal tubules. The demonstration of cellular accumulation by autoradiography supports the hypothesis that an active transport step for hippurates occurs at the peritubular border.

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