Surface charge distribution in normal and transformed rat bladder epithelial cells in vitro.
Cationized ferritin (CF) was used as an ultrastructural marker to study differences in the distribution and density of surface anionic charges between normal and neoplastic cells. In anchorage-independent cell systems, CF induces a redistribution of cell surface receptor-ligand complexes into clusters, patches, and caps on the surfaces of transformed cells, but not on the surfaces of normal cells. In the present report, the authors have, for the first time, extended the CF labeling studies to a system of anchorage-dependent, rat bladder epithelial cell lines: normal RBTC cells and RBTCC-8 carcinoma cells. Cells were grown to confluency and labeled with 500 micrograms/ml CF for 3 minutes. After completion of CF labeling, cells were incubated for 0, 15, 60, 120 minutes, or overnight and were fixed then with buffered glutaraldehyde for electron microscopy. The results show that (a) CF induces grouping of surface anionic charge sites into patches and clusters on RBTCC-8 carcinoma cells (CF covers 53.86 +/- 2.15% of the plasma membrane), but not on normal RBTC cells (CF covers the entire plasma membrane); (b) CF densities are well correlated to the cell surface sialic acid contents of RBTC (2.42 +/- 0.30 microM/10(9) cells) and RBTCC-8 cells (1.26 +/- 0.25 microM/10(9) cells); and (c) CF-labeled membrane is internalized at equal rates by RBTC and RBTCC-8 cells (30% in 15 minutes; 60% in 60 minutes; 70% in 120 minutes; 100% overnight). These data indicate that CF-induced patching of anionic sites is a surface characteristic that is common to anchorage-dependent and independent tumor cells. Mechanisms of CF patching in neoplastic cells are discussed.
Marikovsky
Y
Y
Weinstein
R S
RS
Coon
J S
JS
Pauli
B U
BU
D000818:Animals; D001665:Binding Sites; D002471:Cell Transformation, Neoplastic / Q000648:ultrastructure; D004847:Epithelial Cells; D033862:Iron-Binding Proteins; D008564:Membrane Potentials; D008854:Microscopy, Electron; D051381:Rats; D011916:Rats, Inbred F344; D011956:Receptors, Cell Surface / Q000378:metabolism; D013499:Surface Properties; D001743:Urinary Bladder / Q000166:cytology* / Q000648:ultrastructure
D033862:Iron-Binding Proteins; D011956:Receptors, Cell Surface; C027293:ferritin receptor