Murine
neuroblastoma cells (clone N-2A) grown in
suspension (spinner cells) or attached on a
plastic surface (monolayer cells) were used in studies of the
phospholipid and
cholesterol composition of whole cells, primary plasma membranes, plasma membranes internalized during phagocytosis of
polystyrene latex beads, mitochondria and microsomes. Monolayer cells contained higher concentrations of total
phospholipid,
phosphatidylserine and
phosphatidylcholine, and lower concentration of
phosphatidylethanolamine than spinner cells. The
cholesterol levels and the relative proportions of the various
phospholipids were similar in both cell types except
phosphatidylethanolamine and
sphingomyelin whose proportions were lower in monolayer cells. The primary plasma membranes of the two cell types differed significantly in the relative proportions of all
phospholipids, except
sphingomyelin, and the
phospholipid to
protein and the
cholesterol to
protein ratios were all higher in the membranes of spinner cells. In contrast to these results, all the
phospholipid to
protein and the
cholesterol to
protein ratios of the internalized plasma membranes were higher in monolayer than in spinner cells, and the proportions of all
phospholipids, except
phosphatidylethanolamine, were similar in both cell types. The membrane distributions of individual
phospholipids and
cholesterol were inferred from comparison of the
phospholipid and
cholesterol compositions of primary plasma membranes and plasma membranes internalized during phagocytosis of
polystyrene beads. The results are consistent with a non-random distribution of most
phospholipids in both spinner and monolayer cells, but the patterns of these distributions were different in the two cell types. With regard to
cholesterol the results are compatible with a random or a heterogeneous distribution. All the
phospholipid to
protein ratios of the mitochondrial fraction of both cell types were lower than those of the plasma membranes. However, these ratios of the microsomal fraction were higher than those of the plasma membranes of monolayer cells, whereas they were comparable, with a few exceptions, to those of spinner cell membranes. The
cholesterol to
phospholipid molar ratios of plasma membranes were 6.4 and 4.3 fold greater than those of the mitochondrial and microsomal fractions, respectively.