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Abstract
In order to obtain a better understanding of the “periodic-acid-Schiff” reaction, also known as the “periodic-acid fuchsin-sulfurous-acid” reaction, three types of investigations were carried out
1) The Schiff reagent was replaced by other aldehyde reagents: benzidine or o-dianisidine. There was no significant change in the histological distribution and intensity of the reactions occurring after periodic acid oxidation.
2) Periodic acid was replaced by another oxidizing agent: lead tetraacetate (dissolved in acetic acid). There was no significant change in the histological distribution of the reactions with the Schiff reagent, but some change in their intensity. It was concluded that 1,2-glycols and a-amino alcohols play the main role in the reactions with both oxidants. The presence of α-hydroxy acids in some types of mucous cells is suggested by the results with lead tetraacetate.
Incidently, glycogen and starch are not sufficiently oxidized by lead tetraacetate (in acetic acid) at room temperature to give positive reactions with the Schiff reagent, while cellulose and other periodic-acid-Schiff reactive substances are.
3) The staining of films of presumed reactive substances with the periodic-acid-Schiff technic C O the intense reactivity of many polysaccharides, mucopolysaccharides and mucoproteins, but not of ordinary proteins. (Hyaluronic and chondroitin sulfuric acid are, however, not reactive in vitro).
In conclusion, the periodic-acid-Schiff technic consists of an oxidation of 1,2-glycols and a-amino alcohols to produce aldehyde groups, which are then stained by the Schiff reagent. The “film test” reveals that these radicals are present in certain polysaccharides, mucopolysaccharides and mucoproteins.
