Filterability and Mechanisms of Excretion of Certain Dyes by the Frog's Kidney

Abstract

This report concerns a correlation of the filterability of certain dyes with the manner of their excretion by the kidney as tested by the method of perfusion. The details of the technique of this method may be found in previous publications 1 and the results of our present experiments briefly summarized as follows:

Filtration of a series of dyes through collodion membranes gave the following average values of filterability. Phenol red, 100%; indigo carmine, 90%; toluidin blue, 60%; and neutral red, 35%. Trypan blue was unfilterable as such, but the pink component of the dye passed through the filter in small amounts, and brilliant red was entirely unfilterable.

By perfusion of either the glomerular or the tubular circulation of frogs with these dyes, it was found that phenol red and indigo carmine were eliminated chiefly through the glomeruli. Toluidin blue and neutral red on the other hand were excreted principally by the tubules. Trypan blue was excreted in the relatively short period that our experiments continued only in traces, and these traces passed through the glomeruli most readily and showed the same separation of the components of the dye as was observed in the filtration process, for the urine was pink in color. Brilliant red did not pass through either tubules or glomeruli.

Anesthesia of the tubules and repression of their function during the course of dye excretion increased the rate of elimination of phenol red and indigo carmine, but decreased the rate of excretion of toluidin blue and neutral red. When the glomeruli were damaged in such a way as to increase their permeability, both components of trypan blue escaped into the urine, which assumed the bluish color of the original dye solution.