FACTORS AFFECTING THE STATE OF INJECTED HORSERADISH PEROXIDASE IN ANIMAL TISSUES AND PROCEDURES FOR THE STUDY OF PHAGOSOMES AND PHAGO-LYSOSOMES

Abstract

It was attempted to find conditions at which the localization of injected horseradish peroxidase was preserved at its original sites and artifacts of diffusion and unspecific adsorption of peroxidase to nuclei and cell membranes were prevented. The main factors were thorough fixation of the tissue, osmotic protection with hypertonic sucrose, and avoidance of accumulation, in the fixation medium, of "free" peroxidase, diffusing out of the tissue. Artifacts of adsorbed peroxidase, produced intentionally in tissue of untreated rats by the addition of peroxidase to fixed tissue slices and sections, were compared with the localization in vivo of injected peroxidase in small and large phagosomes and on cell membranes. The uptake of peroxidase by cells of kidney slices in vitro was observed, in confirmation of similar observations by Holtzer and Holtzer (8) with fluorescein-labelled proteins. A procedure for the staining of injected peroxidase in fresh-frozen sections, and a procedure for the double staining of acid phosphatase and injected peroxidase in the same tissue sections, after formaldehyde fixation, was indicated.