Lipopolysaccharide interaction with rabbit erythrocyte membranes.

In this study we have characterized the association of a polysaccharide-deficient, lipid-rich lipopolysaccharide (LPS) with rabbit erythrocytes (RaRBC). With polymyxin B sulfate-mediated hemolysis as a probe, we have shown that Salmonella minnesota R595 LPS interacts with RaRBC in two distinguishable steps. The first step whereby RaRBC exposed to LPS are rendered sensitive to polymyxin B-initiated lysis probably represents absorption of LPS to the RaRBC membrane. We investigated two possible mechanisms for the subsequent time-dependent decrease in response of LPS-treated RaRBC to polymyxin B. We found that the decay in polymyxin B susceptibility of LPS-treated RaRBC cannot be attributed to a decrease in binding of LPS to the RaRBC. On the other hand, our results are consistent with a time-dependent rearrangement of the amphipathic LPS within the lipid bilayer of the RaRBC membrane. In particular, at lower incubation temperatures of RaRBC and LPS, the decay in polymyxin B-induced hemolysis is slower, presumably, because the increased membrane viscosity allows less rapid rearrangement of LPS within the lipid bilayer. A putative hydrophobic intercalation of LPS into a mammalian cell membrane may be of importance in LPS stimulation of responsive cells.