Abstract
Summary and conclusion
A minimal lethal dose of E. coli 0111:B4 endotoxin was injected intravenously into 3 dogs. Two were killed, one 10 and one 90 minutes after endotoxin administration. The third died of endotoxemia in 13 hours. By immunofluorescence, endotoxin was found in patchy distribution throughout the walls of the peripheral vascular system: frequently in the endothelium of capillaries and venules and, extra-cellular as well as intracellular, in the walls of veins; and, on occasion, extracellular and intracellular, in the media of arterioles and muscular arteries.
Endotoxin was also detected in polymorphonuclear leukocytes, both free in the peripheral circulation and in unusual tissue sites; for example, within vessel walls and aggregated in the sinuses of the liver. Particles of endotoxin were frequently seen free in the lumens of blood vessels; in some instances endotoxin appeared to be fixed to the intima of vessels; and masses of endotoxin occasionally completely filled a vascular lumen, most often in renal glomerular capillaries, in the adrenal medullary sinuses, and in liver sinues. Endotoxin was widely distributed throughout the reticulo-endothelial system, including histiocytes. Qualitatively and quantitatively, the distribution of endotoxin within the 3 dogs was similar.
We infer from the presence of endotoxin in blood vessel walls that endotoxin may be acting directly upon these structures to produce the peripheral vascular collapse of lethal endotoxemia.
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