Cultivation of HeLa cells with fetal bovine serum or Ultroser G: effects on the plasma membrane constitution

Abstract

Plasma membranes isolated from HeLa cells cultivated in suspension cultures supplemented with 3.5% fetal bovine serum or 2% of the commercially available serum substitute Ultroser G contained the same amounts of protein, cholesterol, and phosphate on a cellular basis. Minor differences in the plasma membrane fatty acid composition were seen, with the most pronounced alteration observed for palmitic acid, which amounted to 27 and 20% in fetal bovine serum- and Ultroser G- supplemented cells, respectively. Plasma membranes from cells grown with Ultroser G contained almost twice as much phosphatidylethanolamine and displayed two thirds of the phosphatidylcholine content, compared to plasma membranes obtained from fetal bovine serum supplemented cells. The former membranes also showed a 3 times higher specific [3H]acetate labeling of cholesterol, indicating a higher de novo synthesis of cholesterol. Both quantitative and qualitative alterations were revealed among the plasma membrane polypeptides when these were subjected to immuno- and lectin blottings. Fluorescence anisotropy measurements at different temperatures produced similar results irrespective of the growth medium supplement when the plasma membrane specific probe 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene was used on intact cells. However, the average cellular rigidity was higher for Ultroser G supplemented cells, determined with 1,6-diphenyl-1,3,5-hexatriene as a probe.