Binding of Escherichia coli lipopolysaccharide to fasciculata-reticularis and glomerulosa cells evaluated by flow cytometry.

ABSTRACT

Binding of Escherichia coli lipopolysaccharide (LPS) to the two cell types of the adrenal cortex fasciculata-reticularis and glomerulosa cells has been studied by flow cytometry and using fluorescein-labeled lipopolysaccharide (FITC-LPS). The binding characteristics were different in relation to time course and number of binding sites. Both fasciculata-reticularis and glomerulosa cells bound LPS in a specific and saturable process. Fasciculata-reticularis cells showed a higher affinity for LPS binding than glomerulosa cells as deduced from Hill plots. Unlabeled LPS decreased FITC-LPS binding in both fasciculata-reticularis and glomerulosa cells, suggesting competition of both ligands for a limited number of binding sites. Lipid A seemed not to be essential for binding of LPS to fasciculata-reticularis cells. However, serum constituents inhibited FITC-LPS binding to both cell types, possibly due to cell interaction with HDL. The exposure of cells to LPS during cell culture did not modify the number of binding sites, but revealed cell size and surfaces structure changes.