A COMPARISON OF THE STAINING AFFINITIES OF ALDEHYDE-FUCHSIN AND THE SCHIFF REAGENT

Abstract

A comparison is made of the relative affinities of aldehyde-fuchsin and the Schiff reagent for various tissue elements in different states of oxidation. Glycogen, gastric mucus, kidney brush border, intestinal striated border, reticular tissue, gastric parietal cell canaliculi, and Paneth cell granules react with neither aldehyde-fuchsin nor the Schiff reagent without periodic acid or stronger oxidation. Beta cell granules of the islets of Langerhans, keratin, mast cells, elastic fibers, hyaline cartilage, goblet cells, thyroid colloid, argentaffine cell granules, and the acrosomes of spermatozoa are stained by aldehyde-fuchsin without oxidation. None of these tissue elements exhibit a clearly positive reaction with the Schiff reagent under similar conditions. However, elastic fibers, hyaline cartilage, and acrosomes do display a slight coloration. Since the tissue elements which do not stain with aldehyde-fuchsin without previous oxidation act in a similar manner toward both aldehyde-fuchsin and the Schiff reagent, it is assumed that aldehyde groups are responsible for the positive reaction with both these reagents after periodic acid or stronger oxidation. The tissue elements which are stained most intensely by aldehyde-fuchsin without oxidation, i.e., mast cells, hyaline cartilage, and elastic fibers, are those which have been found to contain or to be associated with highly sulfated mucopolysaccharides. Beta cell granules and keratin which after oxidation react strongly with aldehyde-fuchsin, but not with the Schiff reagent, are known to possess a high content of cystine. Since the sulfated mucopolysaccharides possess sulfuric groups and since the dithio bonds of cystine are converted to sulfonic groups on oxidation, it is suggested that these groups may be responsible for the staining of tissue elements by aldehyde-fuchsin when the Schiff reaction is negative. In conclusion, it appears that the reactivities of aldehyde-fuchsin and the Schiff reagent are similar in that they both show an affinity for aldehyde groups, but different in that aldehyde-fuchsin seems to possess an affinity for strong sulfur acids which the Schiff reagent does not.