AJP - Heart and Circulatory Physiology, Vol 258, Issue 5 1498-H1506, Copyright © 1990 by American Physiological Society
Systemic and local effects of endotoxin on canine gracilis muscle vascular conductance
R. F. Bond, C. G. Scott, L. H. Krech and C. H. Bond
Department of Physiology, University of South Carolina School of Medicine, Columbia 29208.
To define the site and mechanism of action that endotoxin has on the
peripheral vasculature, an in situ constant-flow double-canine gracilis
muscle (GM) preparation was utilized. During systemic endotoxemia, one GM
was innervated and the other was denervated during a 30-min intravenous
infusion of 2 mg/kg endotoxin. Significantly increased vascular conductance
(URP) in the denervated GM (106 +/- 26%) occurred compared with the
innervated GM (50 +/- 7%), which suggests that decompensation is not
totally dependent on neural depression. During local endotoxemia, with both
GMs either intact or denervated, one GM was infused intra-arterially for 30
min with a dose of endotoxin calculated to provide a blood concentration
similar to that achieved during systemic endotoxemia, whereas the other GM
was infused with the vehicle. The URPs did not change significantly in
either the saline or endotoxin GMs. Therefore, endotoxin does not act
directly on peripheral vasculature or totally through depression of the
autonomic nervous system. It apparently interacts with a systemically
dependent mechanism to release a vasodepressor substance that is
transported to the peripheral vasculature causing relaxation of vascular
tone.
