Bioassay of the prominent humoral agents involved in endotoxin shock

¹ Neurology Branch, Experimental Medicine Division, Directorate of Medical Research, U.S. Army Edgewood Arsenal Chemical Research and Development Laboratories, Edgewood Arsenal, Maryland

The release of neurohumoral agents into the circulation following the administration of endotoxin has been studied. The use of the isolated vein in circuit with dogs administered a lethal dose of endotoxin permitted measurement of changes in vessel tension and afforded a continuous bioassay of the existing neurohumoral balance. Blocking agents were used to define the agent active at any one time. It appears that histamine or a compound similar to histamine is active in the first phase of shock, with catecholamines playing a predominant supportive role during the second hypotensive phase. The possibility of a parasympatheticlike response causing bradycardia and hypotension is also indicated.

Key Words: stress • histamine • epinephrine-norepinephrine • acetylcholine • hypotension • bioassay in shock • blood vasoactive substances • neurohumoral features of endotoxin shock • gram-negative bacteremic shock

Submitted on November 17, 1964