THE EFFECTS OF BACTERIAL ENDOTOXIN ON LIPIDE METABOLISM

Abstract

Single intravenous injections of bacterial endotoxin (Shear''s polysaccharide) in varying doses invariably produced an elevation in the level of total serum lipids 24 hours after injection. The total serum cholesterol and lipid P were also affected, although they did not change with smaller doses of endotoxin and were rarely elevated to the same degree as were the total serum lipids. The degree of elevation of the serum lipids was apparently related to the amount of endotoxin injected up to a certain point, beyond which there was no further increase. There were 2 types of response to endotoxin by the serum lipids, a moderate increase and an uncontrolled increase. Higher dosages of endotoxin and fasting apparently increased the incidence of the latter response. No direct correlation could be made between serum lipid responses and histologic evidence typical of the generalized Shwartzman reaction following this regimen of endotoxin injection. The Shwartzman reaction did occur with greater frequency and with lower dosages of endotoxin in fasted animals. Animals given repeated injections of endotoxin showed an initial increase in serum lipids followed by a progressive decrease to normal levels as tolerance to the febrile action of endotoxin appeared. The febrile tolerance as well as the unresponsiveness of the serum lipids to endotoxin was abolished by thorium dioxide (thorotrast) in these animals. In similar experiments a "breakthrough" of lipid unresponsiveness to endotoxin was obtained by increasing the amount of endotoxin injected. Some of the implications of these results for the metabolic alterations produced by bacterial endotoxins are discussed.