Chronically prepared rats were injected intravenously with live Escherichia coli in doses from ~105 to ~109 colony-forming units (CFU). Significant dose-related increases in plasma adrenocorticotropin and corticosterone occurred after ~107 CFU. Fever occurred after ~107 CFU but not after ~109 CFU. These responses changed significantly but were not blocked completely when >94% of the viable E. coli was removed from the inoculates. The remaining endotoxin activity in the inoculates resembled lipopolysaccharide (LPS) extracted from the same strain of E. coli on electrophoretic gels. Plasma endotoxin increased for ≤240 min to 5.1 ± 0.9 endotoxin units (EU)/ml after ~107 CFU and to 440 ± 59 EU/ml after ~109 CFU. Endotoxin at ~109 CFU caused death within 24 h that was not predicted by the total activity of endotoxin that was injected. In contrast, extracted LPS with its strain and total activity matched to ~107 CFU mimicked the responses to this nonfatal dose. The total endotoxin activity of the injected bacteria appears to account for the effects of nonfatal doses of E. coli but not for the effects of fatal doses.
|Original language||English (US)|
|Journal||American Journal of Physiology - Regulatory Integrative and Comparative Physiology|
|Issue number||5 41-5|
|State||Published - 1997|
- Bacterial infection
ASJC Scopus subject areas
- Physiology (medical)