THE AUTOFLUORESCENCE OF LYSOSOMES. ITS VALUE FOR THE IDENTIFICATION OF LYSOSOMAL CONSTITUENTS

Abstract

Cytoplasmic inclusions in cells of the nervous system, kidney, liver, alimentary tract and elsewhere have been found to emit a green-yellow fluorescence when irradiated by long ultraviolet light. This study demonstrates conclusively that these autofluorescent inclusions, except for lipofuscin granules, possess acid phosphatase activity and are therefore lysosomes. The deposition of opaque or colored products in lysosomes quenches their fluorescence. This phenomenon has proved useful in localizing other constituents to lysosomes, e.g., PAS-positive substances (Koenig, 1962), intravitally incorporated vital dyes and metals (Koenig, 1963), and acid deoxy-ribonuclease, acid ribonuclease and acid esterase. The fluorescence of lysosomes lends added support to the view that lipofuscin is derived from these organelles.