[Pathophysiological significance of endotoxins].

The biological activities of endotoxin are manifold. Besides the drop in platelets and the biphasic change in the number of leukocytes, severe disturbances in the capillary bed are among the first changes observed following the administration of endotoxin. It is well known that endotoxins cause the release of various vasoactive mediators. According to our results endotoxins enhance the activity of histamine and serotonin; these findings may contribute to a better understanding of the action of histamine and serotonin in the early post-endotoxin phase. The histamine-sensitizing effect of endotoxins is not prevented by antihistamines. Endotoxins and biogenic amines cause similar disturbances in the capillary bed. The changes that are observed in the content of the vessels, the vessel wall, and the perivascular region are the following: slowing down of the blood stream, degranulation of perivascular mast cells, granulocytosis, wall adhering granulocytes, plasma skimming, rouleaux-formation of erythrocytes, reduction in plasticity of many erythrocytes, acanthocytes, acanthocytosis, appearance of spherocytes and microcytes, and formation of massive aggregates of platelets and of microthrombi. Also, occasionally cell aggregates dissolve and as microemboli form new thrombi. Swelling of pericytes, endothelial, and periendothelial cells is observed, and dissociation and deformation of the endothelial cells occur. By means of contact of the vessel contents with the collagen, there is an additional activation of the coagulation system by factor XII possible. The changes of the epithelial lining and the wall adhering cells enhance the narrowing of the vessel lumen. Prestasis and occasionally stasis occur. One observes increased swelling of the endothelial and periendothelial cells, increased permeability of the vessel wall, passage of plasma and occasionally blood cells, especially erythrocytes, through the endothelium and massive microbleedings. While stasis is observed in the nutritive capillaries, in regions where arteriolar-venular shunts exist the flow continues. The systemic blood pressure may therefore remain unchanged during this phase, although the severe disturbances described occur in the capillary bed. Metabolic alterations, especially in the carbohydrate metabolism are mentioned.