Expression and localization of immunoreactive-sialomucin complex (Muc4) insalivary glands

Sialomucin Complex (SMC; Muc4) is a heterodimeric glycoprotein consisting o f two subunits, the mucin component ASGP-1 and the transmembrane subunit AS GP-2. Northern blot and immunoblot analyses demonstrated the presence of SM C/Muc4 in submaxillary, sublingual and parotid salivary glands of the rat, Immunocytochemical staining of SMC using monoclonal antisera raised against ASGP-2 and glycosylated ASGP-1 on paraffin-embedded sections of parotid, s ubmaxillary and sublingual tissues was performed to examine the localizatio n of the mucin in the major rat salivary glands. Histological and immunocyt ochemical staining of cell markers showed that the salivary glands consiste d of varying numbers of serous and mucous acini which are drained by ducts. Parotid glands were composed almost entirely of serous acini, sublingual g lands were mainly mucous in composition and a mixture of serous and mucous acini were present in submaxillary glands. Since immunoreactive (ir)-SMC wa s specifically localized to the serous cells, staining was most abundant in parotid glands, intermediate levels in submaxillary glands and least in su blingual glands. Ir-SMC in sublingual glands was localized to caps of cells around mucous acini, known as serous demilunes, which are also present in submaxillary glands. Immunocytochemical staining of SMC in human parotid gl ands was localized to epithelial cells of serous acini and ducts. However, the staining pattern of epithelial cells was heterogeneous, with ir-SMC pre sent in some acinar and ductal epithelial cells but not in others. This rep ort provides a map of normal ir-SMC/Muc4 distribution in parotid, submaxill ary and sublingual glands which can be used for the study of SMC/Muc4 expre ssion in salivary gland tumors, (C) 2001 Harcourt Publishers Ltd.