Quantitative Histochemistry of the Dog Nephron

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Abstract
Microdissection techniques for the separation of different anatomical segments of the dog nephron from frozen-dried kidney sections are described. Tissue samples thus isolated were suitable for quantitative chemical and enzymatic studies by precise microchemical methods. Trypan blue used as an intravital stain, served to distinguish proximal from distal convolutions, and did not alter the enzymes studied. Quantitative comparisons of water content, lipid content, and the activities of alkaline phosphatase, aldolase, fumarase, phosphohexoisomerase and hexokinase were made. The papilla differed from the other areas in lipid content. Alkaline phosphatase was localized mainly in the proximal convoluted tubules. The other enzymes varied less regularly from area to area. Hexokinase was four times higher in the pars recta of the proximal tubule than in any other area. Inasmuch as glucose reabsorption is believed to occur in the first half of the proximal convoluted tubule, the observed distribution of hexokinase does not further the hypothesis that this enzyme is concerned in glucose reabsorption by the kidney.