Histidine-rich and cystine-rich keratohyalin granules in hamster cheek pouch epidermis. 1. Histochemical examination with a fluorescent thiol reagent (DACM).

Hamster cheek pouch epidermis was examined with a thiol-specific fluorescent reagent [7-(N-dimethylamino-4-methyl-3-coumarinyl) maleimide (DACM)], with the Pauly reagent and by electron microscopy. There were many keratohyalin granules in the cells of the stratum granulosum where they were positively stained with the Pauly reagent, and were fluorescent as a whole, rather than partially, with DACM with or without reduction of disulfide bonds. These data indicate that the whole of a keratohyalin granule was rich in both histidine and cystine. Besides keratohyalin granules, the cellular envelope of the lower half of the stratum corneum showed fluorescence before reduction of disulfide bonds and following reduction of disulfide bonds, the cellular envelope of all stratum corneum cells showed fluorescence. Electron microscopically, keratohyalin granules in hamster cheek pouch epidermis were electron-dense and had a homogeneous structure which was identical to small keratohyalin granules in newborn rat epidermis. Structures corresponding to the single granule of Jessen or to dense homogeneous deposits were not seen. When the specimen was fixed in glutaraldehyde alone, keratohyalin granules consisted of electron-dense and electron-translucent parts. However, the profile was different from that of composite granules seen in both rat tongue epithelium and newborn rat epidermis. Several membrane coating granules were seen in stratum granulosum cells, and marginal band formation also occurred.