Journal of Applied Physiology, Vol 50, Issue 1 178-184, Copyright © 1981 by American Physiological Society
Role of platelet serotonin in the canine pulmonary response to endotoxin
T. L. Murphy, R. C. Allison, I. M. Weisman, D. R. McCaffree and B. A. Gray
There is evidence suggesting a role for platelet serotonin (5-HT) in the
immediate pulmonary response to endotoxin in the dog (J. Appl. Physiol. 23:
47, 1967). To further define this role, autologous canine platelets were
labeled with 5-[14C]HT in vitro and then reinfused. Subsequently
Escherichia coli endotoxin (0.55:B-5, Difco), 2.5 mg/kg, was injected.
Within 5 min dynamic compliance (CL) fell by more than 50%, and nonelastic
resistance (RL) increased by more than 200%. Despite a 95% decrease in
platelet count, less than 10% of the platelet 5-HT was released as
determined by changes in the radioactivity of platelet-poor plasma (PPP)
prepared from both aortic and pulmonary artery blood. As a positive
control, injected of bovine collagen produced a similar decrease in
platelet count that was associated with a significant increase in the
radioactivity of aortic and pulmonary artery PPP. FInally, rapid injection
of a dose of 5-HT equivalent to 25% of the 5-HT in circulating platelets
did not cause a change in CL or RL equivalent to that produced by
endotoxin. From these data we conclude that endotoxin injection does not
cause immediate massive platelet activation and that platelet 5-HT does not
play a major role in the immediate pulmonary response to endotoxin.
