Observations on Mode of Action of Endotoxin in Chick Embryos

Abstract

The present study confirmed the previous observation of Smith and Thomas that the chick embryo becomes refractory to intravenously administered endotoxin during the period from the 11th to the 15 th day of incubation. The magnitude of the change in susceptibility is greater than 10,000-fold. Catecholamines could not be implicated in the lethal action of endotoxin in the chick embryo. Histamine, serotonin and acetyl-choline were not highly toxic for the endo-toxin-susceptible embryos. An anticoagulant, heparin, did not protect against endotoxin, which caused capillary stasis and perivascu-lar hemorrhage in the embryos. Natural antibody against Vibrio cholerae endotoxin could not be detected in the blood during the embryonic state. A marked hypoglycemia resulted following administration of endotoxin and insulin in the younger embryos after a slight delay in the former case. Older embryos, which were markedly tolerant to insulin, developed transient hypoglycemia after insulin administration, but endotoxin caused only slight changes in the level of blood sugar in the older embryos. The versatility and usefulness of the chick embryo for further study of endotoxin phenomena and for bio-assay of endotoxin was emphasized.