lipid-a and triethylamine

The effect of the lipid A moiety of endotoxin on platelet and fibrinogen production was studied in rabbits. Lipid A was infused intravenously in doses ranging from 1 to 100 micrograms/kg body mass; 18 hr later, selenomethionine-75Se was injected intravenously and its incorporation into fibrinogen and platelets determined. Lipid A in saline stimulated fibrinogen and platelet production, but the dose required was 50--100 times that required for an intact endotoxin. Although lipid A solubilized in triethylamine (TEA) was at least 60 times more active in the Limulus amebocyte lysate assay than was lipid A suspended in saline, the sensitivity of platelet and fibrinogen production to solubilized lipid A was increased only twofold. Incorporation of lipid A into liposomes had no effect on its Limulus activity. Lipid A in liposomes continued to stimulate platelet, but not fibrinogen, production. Leukopenia that was induced by lipid A in TEA did not occur when rabbits received the same dose of lipid A in liposomes. Lipid A, like intact endotoxin, can stimulate platelet and fibrinogen production and induce leukopenia but the doses required are high. The low solubility of lipid A in aqueous solutions may be only one factor that determines its biologic activity.

Topics: Animals; Blood Platelets; Dose-Response Relationship, Drug; Endotoxins; Ethylamines; Fibrinogen; Leukopenia; Lipid A; Lipopolysaccharides; Liposomes; Male; Platelet Count; Rabbits

Disaggregation of wild-type and Re chemotype lipopolysaccharides (LPS) has been accomplished by solubilization with triethylamine followed by stabilization with bovine serum albumin in order to determine the degree of aggregation. Solubilization with 1.5% triethylamine was found to be more effective than with lower concentrations, as judged by permeation chromatography. Chromatographic analysis of triethylamine-bovine serum albumin-disaggregated LPS showed a range of particle sizes. Wild-type LPS yielded size classes of 1 X 10(6) to 4 X 10(6) daltons, 250,000 daltons, and 20,000 daltons. Re LPS yielded size classes of 1 X 10(6) to 4 X 10(6) daltons and 20,000 daltons. Untreated LPS was always greater than 4 X 10(6) daltons. Chemical characterization of the size classes revealed 3-keto-2-deoxyoctonate in all size classes and suggests that the O-antigenic side chain length may determine the aggregate size in solubilized LPS.

Topics: Carbohydrates; Ethylamines; Ketoses; Lipid A; Lipopolysaccharides; Molecular Weight; Particle Size; Polysaccharides, Bacterial; Salmonella typhimurium; Serum Albumin, Bovine; Solubility; Sugar Acids