Surface proteins in normal and transformed rat liver epithelial cells in culture

The pattern of surface proteins of different types of normal and transformed rat liver cells have been studied in culture by means of lactoperoxidase-catalysed iodination procedures, followed by SDS-gel electrophoresis. The cells examined were primary cultures of epithelial liver cells, long-term cultures of epithelial liver cells, in vitro transformed epithelial liver cell lines and liver tumour-cell lines; mesenchymal cells from liver and skin were also examined. The principal surface proteins of primary cultures of epithelial cells from adult or neonatal rats had components with mol. wts of 140,000-160,000, 100,000 and 40,000-70,000. A band that had the same position as fibronectin from mesenchymal cells was also present and this band, as well as other iodinated components, were less sensitive to trypsin than fibroblastic fibronectin. A similar pattern of iodinated proteins was seen in long-term cultures of epithelial liver cells, with a great reduction in the number and intensity of the bands in the mol. wt region below 100,000. Almost all the in vitro transformed and tumour epithelial cell lines contain a protein with a mol. wt 135,000 as one of the major iodinated bands, and in contrast to the observation in transformed fibroblasts, the fibronectin was retained by most of these transformed cell lines.