Pulmonary pressor responses in sheep to chemically defined precursors of E. coli endotoxin

The toxicity of various monosaccharide and disaccharide endotoxin precursors has now been studied in sheep. We measured the early pulmonary arterial pressure responses after injections of the monosaccharides lipid X (2,3-diacylglucosamine 1-phosphate) and MAGP (2-monoacylglucosamine 1-phosphate), of the tetraacyl disaccharide diphosphate precursor of lipid A, IV-A (Federation Proc. 43: 1567, 1984), and of Escherichia coli bacterial endotoxin (lipopolysaccharide). We also measured the response of lipid X after prior administration of indomethacin and MAGP. Lipid X, at a total cumulative dose of 40 micrograms/kg, produced an immediate, but transient dose-dependent pulmonary arterial vasoconstrictive response. MAGP, at a total dose of 40 micrograms/kg, had no pulmonary pressure activity but did increase extravascular lung water and produce some histological changes in the lung. Disaccharide precursor IV-A, at a total dose of 40 micrograms/kg, produced an immediate dose-dependent pulmonary arterial vasoconstrictive response that was prolonged for greater than 2 h. E. coli endotoxin caused a delayed (15-min) increase in the pulmonary arterial pressure but one that also persisted for greater than 2 h. Prior administration of indomethacin blocked the pulmonary pressor activity of lipid X, whereas prior administration of MAGP increased both the magnitude and the duration of the pulmonary pressure response of lipid X. We conclude that the initial pulmonary hypertension seen after lipid X injection may involve cyclooxygenase-dependent formation of prostaglandins and that the genesis of this pulmonary pressor activity is at least in part dependent on the ester-linked hydroxymyristoyl moiety at position 3 of the lipid X molecule.(ABSTRACT TRUNCATED AT 250 WORDS)