Changes of glycolipids dependent on cell density of Ehrlich ascites carcinoma cells

Abstract

The glycolipid composition of Ehrlich ascites carcinoma cells was found to depend strongly on the cell density of the suspension. The general trend observed upon dilution of the cell suspension was a reduction of the less complex gangliosides GM3 and G,, with concomitant increase of the more complex gangliosides, especially GM1. The increase of the content of ganglioside GMi upon dilution was accompanied by a comparable decrease of the content of its immediate precursor, asialo-GM1, whereas the content of other neutral glycosphingolipids did not change very much. When the cell suspension was diluted with medium conditioned by dense cells the ganglioside profile of the diluted suspension remained similar to that of the dense cell suspension. It is postulated that the medium conditioned with dense cells contains a transferable factor inhibiting sialylation of asialo-GM,.Glycolipids are involved in cellular recognition, cell growth, and receptor events [1]. For cells growing in culture on solid supports the synthesis and catabolism of glycolipids has been shown to depend on the cell density. For example, the ganglioside composition of BHK and NIL cells has been found to change on the stage of confluency [2] whereas no cell-densitydependent changes were observed with several strains transformed by oncogenic viruses [3]. On this ground it has been suggested that cell-density-dependent changes of glycolipid composition are linked with contact inhibition of growth and development [4-51. No comparable data are available for single living cells. A convenient model for studying cell density dependence in single living cells is the Ehrlich ascites carcinoma (EAC). Earlier the structure of the neutral glycosphingolipids and gangliosides of these cells has been established [6, 71.111 the present work we investigate the changes in the glycosphingolipid composition of EAC cells occurring during incubation of the cells at different cell densities. We demonstrate the glycolipid composition of the cells to depend strongly on the cell density and present data suggesting that at higher densities the biosynthesis of gangliosides is impaired, possibly due to the presence of a humoral sialyltransferase-inhibiting factor. To our knowledge this is the first demonstration of cell density dependence of the glycolipid composition in single living mammalian cells. MATERIALS AND METHODSAll chemicals were of analytical reagent grade, and solvents were redistillated prior to use. CellsEAC cells taken from mature male CBAXC,~BI/F, mice maintained for 7 days were used. The ascites fluid was drown off from the peritoneal cavity and centrifuged at 500 revjmin for Smin. The cell pellet was washed thrce times with phyAbbreviations. EAC, bhrlich Ascites Carcinoina; Ganglioside nomenclature according to the recommendations of IUPAC-IUR Commission on Biochemical Nomenclature (nomenclature system of Svcnnerholm) [15].siological salt solution and suspended in Eagle's mediumiphysiological salt solution (1 : 1, viv) to obtain a volume of cell suspension e...

Growth- and Development-Dependent Expression of Gangliosides in Rat Hepatocytes and Liver Tissues

“…Reduction of GM3 with increasing cell density is observed in the presence of EGF. It has been reported that the cell density of a culture influences the expression of gangliosides in various cell types, including hamster kidney fibroblasts (Hakomori, 1970), mouse 3T3 fibroblasts (Yogeeswaran and Hakomori, 1975), human diploid fibroblasts at early passages (Ohsawa, 1989), mouse embryonic cells (Langenbach and Kennedy, 1978), human glioma (Liepkalns et al, 1981), mouse neuroblastoma cells (Schengrund and Repman, 1982;Kadowaki et al, 1990), and Ehrlich ascites carcinoma cells (Prokazova et al, 1984). Many of these cells exhibit ganglioside patterns characterized by increased proportions of di-and/or polysialo gangliosides with reduction of simpler ganglioside species at higher cell density.…”