Functional Sites in Normal and Segmentally Necrotic Renal Tubules

Abstract

Intraperitoneal or lymph sac (frog) injections of 1% solutions of ferric ammonium citrate and sodium ferrocyanide were made in 50 rats, 10 turtles and 100 frogs. The presence of either salt or both in the kidney of these animals, depending on whether one or the other or a mixture was injected, was revealed by the Prussian blue reaction. In the kidney of the rat the cellular excretion of ferric iron is sharply localized in a segment of the proximal convolution, 2-3 mm. long, beginning 6-8 mm. from the glomerulus (Figs. 2 and 3, portion marked by a bracket). The excretion of ferrocyanide is not similarly localized. To the extent that it may be excreted by the cells of the proximal convolution, all of them appear equally active. When the 2 salts are injected as a mixture, the locus of excretion of both is the same as that stated for the excretion of the ferric salt alone. A probable explanation for this peculiarity is to appear in another publication. The accuracy of the determination of the presence and extent of this locus is the result of macerating and mounting the renal unit (Fig. 3) of the variously treated animals parallel to each other on a glass slide and studying them unstained under the microscope.

The characteristic appearance of P. blue in finely particulate form in the cells of that portion of the proximal convolution active in the excretion of iron is shown by the darker, stippled-appearing cells of the tangential section (Fig. 4, “Y”). In the kidney of the turtle and frog, the cellular excretion of both ferric iron and ferrocyanide is shared equally by the cells of the entire proximal convolution and the appearance of P.