title: Lipid A dependence of the ocular response to circulating endotoxin in rabbits.
abstract: The effects of bacterial lipopolysaccharides on ocular vascular permeability were measured after their intravenous injection in rabbits. Alterations in ocular vascular permeability were quantitated by the accumulation of 125I-labeled albumin in the enucleated eye compared with that in heart blood (ocular albumin space). Two lipopolysaccharides extracted from Escherichia coli O111:B4, one with high lipid A content and one with high polysaccharide content, were tested initially, and the one with greater lipid A was 200 times more effective in producing an alteration in ocular vascular permeability. Lipopolysaccharide from a rough strain, Salmonella minnesota (R595), containing lipid A primarily, as well as a purified lipid A extracted from +595, were also effective. But an extract of the protein associated with lipid A was without significant effect. In vitro pretreatment of the lipopolysaccharides with polymyxin B, an inhibitor of the biological activity of lipid A through direct binding, could abrogate the ocular response. These results indicate the paramount importance of the lipid A moiety in the ocular response to circulating endotoxin.
mesh_terms: D000818:Animals; D002199:Capillary Permeability / Q000187:drug effects; D004731:Endotoxins / Q000494:pharmacology*; D004926:Escherichia coli; D005123:Eye / Q000098:blood supply / Q000187:drug effects*; D008050:Lipid A / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D011112:Polymyxin B / Q000494:pharmacology; D011817:Rabbits / Q000502:physiology*; D012475:Salmonella
chemical_list: D004731:Endotoxins; D008050:Lipid A; D008070:Lipopolysaccharides; D011112:Polymyxin B