A study of morphological and chemical properties of keratohyalin granules.

Abstract

Cytoplasmic fibrils and keratohyali# granules have been long considered to play an important role in keratinization of the mammalian epidermis. Cytoplasmic fibrils (tonofibrils) occur in all types of epidermal cells (1, 2, 3,.4). Those present in basal, spinous or granular cell types are assumed to represent macromolecular pre-units of fibrous epidermal keratin (5). The cytoplasmic fibrils are 50 to 100 A in diameter (6, 7, 8, 9, 10, 11, 12, 13, 14, 15), reveal an alpha keratin structure (3, 4, 16) and are rich in -SH groups (16, 17, 18, 19, 20). In cornified cells -S-S- bonds have been identified in addition to -SH groups, indicating that the horny component is partially stabilized by strong covalent bonds.