Affinity of Neutral Red for Cells with Basophilic Cytoplasm

Abstract

IN earlier studies^1,2 it was found that within half an hour of mice being injected with the dye neutral red, the cytoplasm of the exocrine cells of the pancreas became diffusely and homogeneously pink. A short time later, small reddish granules, the so-called ‘neutral red granules’, appeared. Shortly after injection these granules were discrete, but later took the form of aggregates immiscible with the cytoplasm. The single granules were about 0.7µ in diameter, the aggregates 2.5–3µ, and both were confined to the basophilic portion of the cell between the zymogen granules and the basement membrane. They did not occur among the zymogen granules and were never intranuclear. Vacuoles with these characteristics which might have been coloured by entrance of the dye into the cell were never observed in pancreas exocrine cells from animals not given the dye and it was concluded that the neutral red granules were ‘new’ formations. By the application of two techniques, Janus green³ in living cells and Altmann⁴ in fixed tissue, it was possible to distinguish the neutral red granules from apparently normal mitochondria.