THE XANTHYDROL REACTION FOR PYRROLES AND INDOLES IN HISTOCHEMISTRY: ZYMOGEN GRANULES, LENS, ENTEROCHROMAFFIN AND MELANINS

Abstract

Zymogen granules of the pancreas, peptic and salivary glands, eosinophil leucocyte granules, lens fibers, and sometimes Paneth cell granules give a violet color with xanthydrol. Muscle and various cytoplasms react weakly, collagen, clastin, keratin, chromaffin, enterochromaffin, melanin, bone, cartilage and mucus do not react. The positive reaction seems largely assignable to the presence of tryptophan. In vitro reactions occur both with various indoles and pyrroles and also with certain polyphenols. The tissue reaction is attenuated and finally abolished by chromation and is inhibited by adequate iodination and by adequate peracetic acid oxidation. Formaldehyde condensation with tryptamine only slightly weakens its reactivity to xanthydrol, and the positive reactions of carbazole and tetrahydronorharman also argue that formaldehyde should not prevent the reaction of 5-hydroxytryptamine to xanthydrol. Hence the identification of the enterochromaffin substance as such with 5-hydroxytryptamine seems increasedly improbable.