The effects of bacterial endotoxin on lipide metabolism. I. The responses of the serum lipides of rabbits to single and repeated injections of Shear's polysaccharide.

Single intravenous injections of Shear's polysaccharide in varying dosages invariably produced an elevation in the levels of the total serum lipides 24 hours after injection of endotoxin. The total serum cholesterol and lipide phosphorus 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 lipides. The degree of elevation of the serum lipides was apparently related to the amount of endotoxin injected up to a certain point, beyond which there was no further increase. There were two types of response to endotoxin by the serum lipides, 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 lipide 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 lipides 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 lipides to endotoxin was abolished by thorium dioxide (thorotrast) in these animals. In similar experiments a "breakthrough" of lipide 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.