THE EFFECT OF SAPONIFICATION UPON CERTAIN HISTOCHEMICAL REACTIONS OF THE EPITHELIAL MUCINS OF THE GASTROINTESTINAL TRACT

An increase in periodic acid-Schiff reactivity after saponification has been demonstrated in the gastrointestinal tract mucins of man, rat, rabbit and guinea pig. Tins pH-dependent phenomenon is independent of fixation and processing since it occurred in cryostat sections of fresh and formalin-fixed tissue and in paraffin sections of tissues fixed in eight different fixatives. In man and rat this effect occurs at the level of the ileocecal valve and below; in guinea pig it is confined to the large intestine and rectum; while in rabbits it occurs in Brunner's glands, the ileocecal valve and below. In man the increase is found throughout the crypts whereas in rabbits the effect is seen mainly at the luminal end; in rats it is seen largely at the base of the crypts; and in guinea pigs it is variable. This effect, due to an increase in the number of 1:2 glycol groups, is accompanied in man, rat and guinea pig by an increase in basophilia due to the presence of sulfate and/or other highly acidic groups.