Modification of serotonin and histamine release after E. coli endotoxin administration

¹ Department of Medicine, University of Minnesota Medical School and University Hospitals, Minneapolis, Minnesota

Platelet counts, serotonin, and histamine concentrations were studied after administration of E. coli endotoxin to rabbits in five experimental models. These included tolerance, immaturity, and pretreatment with heparin, warfarin, and epsilon-aminocaproic acid (EACA). Platelet counts and whole blood concentrations of serotonin and histamine were similar to values obtained in control rabbits given only endotoxin. Immediate increases in the concentration of serotonin and histamine in platelet-free plasma were inhibited in animals pretreated with warfarin and heparin. Tolerant animals, immature animals, and animals given EACA showed increases of plasma amines compared with saline-treated controls, but tolerant and immature animals showed significantly smaller elevations in plasma amines than adult controls given endotoxin. Elevations of plasma amines were absent 2-hr after endotoxin. The results are consistent with the hypothesis that rapid amine release in vivo occurs secondary to the action of thrombin on platelets. The occurrence of thrombocytopenia without increases in plasma amines was seen in certain cases. Tolerance and immaturity modify, but do not prevent immediate amine release.