Immunohistochemical Identification of Cytokeratins in the Rat Submandibular Salivary Glands during Ontogenesis

Cytokeratins (CK) are a group of proteins comprised of at least 20 different skeletal polypeptides specific for simple and complex epithelia of almost all tissues. Until recently only a few antibodies for cytoskeletal proteins were available and thus it was very difficult to visualize all the components of postnatal cytodifferentiation of salivary glands. Therefore, morphologic and immunophenotypic features of the CK polypeptides, have been analized within the rat submandibular salivary glands (SSG) during postnatal development. SSG were obtained from 1, 30 and 60 days old, male, AO rats. Streptavidin-biotin immunoperoxidase method was used for immunohistochemistry. Cryostat sections were fixed in acetone and incubated with monoclonal antibodies (mAbs) which specifically react with CK polypeptides (CK7, CK8, CK18, CK kidney, K8.12, K8.13) and rat epithelium (PT13D11). Immunohistochemical analysis of the rat SSG showed phenotypic heterogeneity of particular components of this gland during postnatal development. Regarding CK profiles it was shown that epithelial cells of the acini expressed CK18, whereas epithelial cells of the duct expressed K8.12 and K8.13 mAbs. Epithelial cells of the acini were not stained by K8.12 and PT13D11 mAbs. Intercalated ducts were strongly CK kidney+ and PT13D11+. Myoepithelial cells of the acini were stained by K8.13 mAbs, whereas these cells were not stained by mAbs specific for simple epithelia. This immunohistological study showed that the heterogeneity expression of CK polypeptides might also be useful to further understand the origin of epithelial SSG celss, as well as their development and function.