Effect of endotoxin tolerance on the lead acetate-induced endotoxin hypersensitivity of rats

Inverse relationship between the susceptibility of lipopolysaccharide (lipid A)-pretreated mice to the hypothermic and lethal effect of lipopolysaccharide

Mice pretreated (day 0) by a single injection of lipopolysaccharide (LPS) responded with hypothermic tolerance to (LPS) challenge on day 1 and with hypothermic hyperreactivity to LPS challenge on day 4. Reciprocally, mice pretreated similarly but with a higher challenge dose were hyperreactive with respect to LPS lethality on day 1, but highly tolerant to lethality when challenged on day 4. Hyperreactivity to LPS lethality (day 1) was evident from an accelerated onset of death as well as from a reduced 50% lethal dose in pretreated mice, the level of hyperreactivity being more pronounced with higher LPS pretreatment doses. Lethal hyperreactivity, however, was only seen after challenge with a 50% lethal dose of soluble LPS. In contrast, protection to lethality occurred after challenge with a 50% lethal dose of insoluble LPS (day 1). Tolerance to LPS lethality in mice was observed on day 4 after pretreatment with one (day 0) or four daily injections of LPS. Since reciprocal hyperreactivity (day 1) and cross-tolerance to lethality (day 4) could be achieved by treatment with Salmonella smooth- or rough-form LPS as well as with free lipid A, it was concluded that lipid A represents the active principle of LPS in inducing both hyperreactivity and tolerance to the lethal effect of LPS.

Porcine salmonellosis. II. Production of the generalized Shwartzman reaction by intravenous injections of disintegrated cells of salmonella cholerae-suis

Three pigs were given intravenous injections of disintegrated cells of Salmonella cholerae-suis. One of these pigs developed macroscopic bilateral renal cortical necrosis. Histologic examination revealed, besides total cortical parenchymal necrosis, also severe vascular injury, characterized with fibrinoid necrosis of the vessel walls and fibrin thrombi within their lumina. These findings were interpreted as a result of a generalized Shwartzman reaction, provoked by the action of bacterial endotoxin.

Effect of bile acids on the intestinal absorption of endotoxin in rats

The absorption of tritium-labeled Escherichia coli O89 Westphal-type endotoxin from the peritoneal cavity of rats was diminished by bile by 23% and by sodium deoxycholate by 47%, respectively. Practically, there is no endotoxin absorption from the intestinal tract of normal rats. The bile duct of rats was chronically cannulated for experimental purposes. A significant amount of perorally administered endotoxin absorbed from the intestinal canal into the blood in the rats treated thus. Absorption was demonstrated by the lethal effect of endotoxin on rats previously hypersensitized by lead acetate, and by the radioactivities found in the blood samples. The intestinal absorption of endotoxin in rats, rendered bile-deficient, may be prevented by sodium deoxycholate. Supported by their experimental findings, we emphasize the important role of bile acids in the defense mechanism of the macroorganism against bacterial endotoxins.

Effect of endotoxin on the serum ribonuclease activity in rats

The effects of endotoxin shock, endotoxin tolerance, and lead acetate plus a minute amount of endotoxin on the serum ribonuclease activity of rats was measured. Changes in serum ribonuclease activity after various entoxin treatments could be a primary effect or a secondary effect of the damaging effect of endotoxin.