The constituents of keratohyalin granules of newborn rat epidermis under an electron microscopy.

Three-day-old rat skins were treated either by the freezing--thawing method or by the tetraphenylboron technique. After the former procedure, keratohyalin granules were solubilized, leaving empty spaces with an electron-dense or less dense rim. Particles roughly 200 A in diameter, which were either electron-dense or less dense, were observed in the empty spaces and also seen detaching from the rim. After the freeze--thaw procedure, two types of keratohyalin granule were observed. The one is the same electron-dense granule as keratohyalin granules in vivo and the other is the granule, the electron density of which was identical with tonofilaments. Both granules were granular rather than fibrous in structure.