Altered composition of membrane glycoconjugates in rat hepatoma tissue culture cells after dexamethasone treatment or in vivo growth.

HTC cells2 are characterized by the same distinct set of gly coproteins and glycolipids. This set of glycoconjugates is dif ferent from that of Reuber H-35 cells or normal hepatocytes (3, 8). Most of the glycoproteins and glycolipids are turned over as units with half-lives of 75 to 100 hr (3, 28). The quantitative and qualitative composition of membrane glyco proteins is quite stable; for instance, no important differences in glycoprotein composition could be detected between HTC cells grown in suspension and in monolayer culture or those grown at low and high cell density (3),3 There are, however, reports that changes in plasma membrane function, such as adhesiveness (2), amino acid transport (17, 22), and secretion of plasminogen activator (7), occur when these cells are treated with glucocorticoids. Another quite unexpected observation is that HTC cells, which normally exhibit only very loose cell-cell interaction, form solid tumors rather than ascites-type tumors when grown i.p. in rats. This alteration in cell affinity suggests possible structural reorganization at the cell surface involving both glycoproteins (21) and glycolipids (i 3). In the present paper, we examined the changes in membrane glycoconju gates which occur when cell growth is influenced by hormones or by in vivo environment. We found that several qualitative as well as quantitative alterations in the composition of the mem brane glycoproteins occur when HTC cells were either treated with dexamethasone or grown in vivo in rats. Under the same experimental conditions, the glycolipid pattern remains rela tively constant.