AJP - Heart and Circulatory Physiology, Vol 235, Issue 2 150-H156, Copyright © 1978 by American Physiological Society
Endotoxin and myocardial failure: role of the myofibril and venous return
F. D. Bruni, P. Komwatana, M. E. Soulsby and M. L. Hess
The effects of gramnegative endotoxin-induced myocardial failure in the
pentobarbital-anesthetized dog were examined by monitoring its influence on
cardiac myofibrillar ATPase activity. Myofibrils were isolated from endo-
and epicardial portions of the left ventricular wall. ATPase activities
were determined in animals treated with 4 mg/kg endotoxin and monitored 5
h, in animals monitored for 5 h without endotoxin (controls), and in
animals implanted with a unilateral femoral shunt and given endotoxin. No
differences were seen in the activities between the endo- and epicardial
portions of any preparation. Activity was significantly depressed in
endotoxemic animals. Increasing venous return by 313 +/- 71 ml/min
significantly increased coronary flow by reducing coronary vascular
resistance and prevented any observed depression of myofibrillar ATPase
activity. In in vitro studies, adding endotoxin directly to a myofibril
preparation did not modify normal activity. It appears that the mechanical
and myofibrillar dysfunctions are due to the action of endotoxin at sites
not associated with the actomyosin ATPase, but may be due to the production
of an intermediary agent in concert with a decreased venous return.
