Abstract
The presence of laminin and type-IV collagen in the basement membrane of the rat incisor enamel organ at different stages of odontogenesis was demonstrated by means of pre-embedding immunoperoxidase method.Immunoreaction for laminin and type-IV collagen was observed in the basement membrane and in the fibrillar layer attached to the membrane demarcating the inner enamel epithelium from the dental papilla. Occasional reaction products for laminin and type-IV collagen localized in the rough endoplasmic reticulum cisternae in cells of the inner enamel epithelium and dental papilla indicated cooperative production of basement membrane components. The basement membrane of differentiating ameloblasts showed reactions for laminin and type-IV collagen, though the intensity was consistently lower than that of reactions in the inner enamel epithelium. These reactions gradually became indistinct and discontinuous and disappeared entirely prior to dentin formation. At this time, positive reaction products were observed in the deep, irregular invaginations and coated pits in the distal ends of differentiating ameloblasts, indicating resorption of basement membrane components. The basement membrane-like structure appearing between the maturing ameloblasts and the enamel surface reacted positively for laminin. Occasional occurrence of reaction products in rough endoplasmic reticulum of maturing ameloblasts indicated laminin production. No reaction products for type-IV collagen, however, occurred in the basement membrane-like structure. Positive immunoreactions were observed in the basement membrane demarcating the outer enamel epithelium and the papillary layer from the dental sac. Basement membranes of blood capillaries that had penetrated into the papillary layer also showed intense immunoreaction. Reaction products were frequently seen in the perinuclear spaces and the rough endoplasmic reticulum cisternae of outer enamel epithelium cells but not of papillary layer cells.
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