The Ca(2+)-binding proteins S100A1, S100A2, S100A4, S100A6 and S100B were evaluated immunohistochemically in normal skin and skin appendage tumours. Epidermal basal cells, epithelial cells of sebaceous glands, hair follicle sheet epithelia and eccrine duct reacted strongly with an antiserum against human S100A2 but were nonreactive or weakly reactive to S100A1, S100A4, S100A6 and S100B. Varying types of skin appendage tumours and most peripheral cells in tumour nests of basal cell carcinoma and squamous cell carcinoma showed positive S100A2 immunoreactivity in neoplastic cells corresponding to basal cells but were nonreactive or faintly reactive for other S100 proteins. Langerhan's cells and melanocytes were labelled by S100B. Basophilic cells of calcifying epithelioma were occasionally stained with S100A2 antiserum. Eccrine poroma did not react with any S100 antiserum. Mixed tumours of the skin containing neoplastic myoepithelial cells stained strongly for S100A2 and S100B but only faintly for S100A1, S100A4, S100A6. This is the first report on selective evaluation of different S100 proteins in normal skin. These antibodies are valuable tools for better characterization of skin appendage tumours.

S100 proteins are calcium-binding proteins of the EF-hand superfamily and are involved in the regulation of a number of cellular processes. The present study deals with the immunohistochemical expression of S100A1 and S10100A6 in the rat submandibular and sublingual glands during postnatal development from day 0 to 12 weeks. Expression of S100A1 was particularly concentrated in pillar and transition cells in the granular convoluted tubule (GCT) and in striated duct cells of the submandibular gland age 4 weeks to maturity. None or only weak staining for S100A1 was observed in the duct segment at 0-5 days. On the contrary, immunostaining of S100A6 was present in proacinar cells in undifferentiated submandibular gland at age 3 days to 2 weeks. S100A6 immunoreactivity in rat submandibular gland coexisted with chromogranin reactivity. It is possible that S100A6 regulates secretion of chromogranin in proacinar cells. Secretion of growth factors and biologically active peptides in the GCT are regulated by calcium signals, and S100A1 may be involved in the secretory mechanism of granular cells. S100A1 and S100A6 are potentially of great importance in secretory functions of granular cells and proacinar cells, as well as in rat salivary glands.

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