DISTRIBUTION OF S-100 PROTEIN AND ITS SUBUNITS IN BOVINE EXOCRINE GLANDS

The distribution of S-100 protein and its alpha- and beta-subunits in bovine exocrine glands was studied by indirect immunohistochemistry. T he entire spectrum of salivary glands, glands of the respiratory tract , intestinal glands, male and female genital glands, and skin glands w as examined. S-100 and its beta-subunit were identified in most serous secretory cells of mixed salivary glands, although secretory acini in some serous glands remained unreactive for these antigens. Mucous cel ls were constantly negative; mucoid cells were positive in the lacrima l and Harderian gland. The alpha-subunit of S-100 protein was identifi ed in serous cells but the staining reaction was faint. Subunits of S- 100 showed a characteristic distribution along the excretory duct syst ems of compound glands: S-100 and the beta-subunit were present in int ercalated duct epithelium, while striated duct epithelium stained for S100-alpha. Therefore, it is suggested that S100-alpha is related to r esorption and secretion in striated ducts, while S100-beta may govern acinar exocytosis and probably regulates proliferation and differentia tion of glandular cells. Differing staining intensities for S-100 and its subunits in secretory cells of exocrine glands most probably indic ate functional differences with regard to secretory activity and the c ell cycle.