Sulphur in different types of keratohyalin granules: a quantitative assay by x-ray microanalysis

The elemental composition of keratohyalin granules from the interpapillary and papillary lingual epithelium and the oesophageal epithelium of the rat were studied by X-ray microanalysis in an EMMA-4 analytical electton microscope, equipped with an energy dispersive detector. A quantitative assay of the sulphur concentration in keratohyalin granules was performed, using a suitable sulphur standard. The results demonstrate that different types of keratohyalin granule have different compositions. Single granules - a type of keratohyalin granule present in both nuclei and cytoplasm of the epithelial cells - are rich in sulphur, having a content of 3·6-3·8%. Another type of keratohyalin granule - composite granules - contains a sulphur-rich component and a sulphur-poor component. The sulphur-poor component contains 0··8-1·4% sulphur. It is suggested that the sulphur-rich keratohyalin granules are involved in the deposition of the peripheral envelope protein of cornified cells.