Segregation of an Intravenously Injected Protein by "Droplets" of the Cells of Rat Kidneys

Abstract

A simple, quantitative method was developed to study the distribution of an intravenously injected protein in cell homogenates and sub-cellular fractions. The method consists in injecting a plant enzyme, horse-radish peroxidase, as a tracer, and in analyzing the concentration of the injected enzyme colorimetrically. The assay is a modification of the test for cytochrome c oxidase described previously, and it utilizes the transformation, by oxidative enzymes, of dimethyl-p-phenylenediamine into a red pigment of semi-quinone nature. By applying this method, it was shown that the concentration of the injected plant enzyme was many times higher in isolated droplet fractions than in the other fractions of the kidney homo-genate.