DISTRIBUTION OF BASAL LAMINA TYPE-IV COLLAGEN AND LAMININ IN NORMAL RAT TONGUE MUCOSA AND EXPERIMENTAL ORAL-CARCINOMA - ULTRASTRUCTURAL IMMUNOLOCALIZATION AND IMMUNOGOLD QUANTITATION

The relationship of basal lamina, a form of specialised extracellular matrix which separates epithelial cells and other cell types from adja cent stroma, to the behaviour of malignant neoplasms of epithelial ori gin is not well understood. However, it is widely acknowledged that th e properties of local invasion and metastasis of carcinomas are linked to extracellular matrix (including basal lamina) changes. In the pres ent study, the distribution of the major basal lamina components, type IV collagen and laminin, in normal rat tongue mucosa and experimental ly induced oral carcinomas was investigated using post-embedding immun ogold techniques and electron microscopy. The expression of these comp onents was also quantitatively analysed using morphometry and immunocy tochemistry. Results indicated that type IV collagen and laminin were confined to the lamina densa of normal oral epithelial basal lamina, a nd that both components were also detected in the lamina densa of basa l lamina associated with carcinomas, and in the extracellular matrix o f tumours. Furthermore, laminin was detected within stromal fibroblast s in normal tissues and experimental carcinomas. Quantitative analysis indicated that expression of laminin was significantly increased in c arcinomas. In contrast, type IV collagen expression was significantly decreased. The quantitative changes observed in the two basal lamina c onstituents may be related to the process of tumour invasion, reflecti ng altered metabolic activities of tumour and stromal cells. These obs ervations may be of use in understanding the architectural characteris tics of oral mucosa basal lamina and in assessing the malignant potent ial of epithelial dysplasias or ''premalignant'' lesions.