Effects of increases in carboxyhemoglobin percent saturation and tissue hypoxia on carbon monoxide binding to canine skeletal and heart muscle extravascular tissue

This article provides for the first time in a mammal quantification of some physiological parameters that determine carbon monoxide (CO) binding to skeletal and heart muscle extravascular tissue hemoproteins during normal and CO poisoning conditions. This is important information because toxicity occurring during CO poisoning is determined in part by CO binding to these proteins that results in detrimental changes in cellular metabolism. The major goal of this article was to quantify relationships of the carboxyhemoglobin % saturation, a calculated tissue P CO , and tissue hypoxia to the binding of carbon monoxide (CO) to canine skeletal and heart ventricular muscle extravascular (EV) tissue under normal conditions and during CO poisoning scenarios. These data are relevant to CO poisoning because CO bound to EV cellular hemoproteins evoke metabolic changes that produce toxic effects. Skeletal and heart muscle EV CO contents were calculated from data obtained from biopsies performed on living anesthetized dogs reported in previous publications (Coburn RF, Mayers LB. Am J Physiol 220: 66–74, 1971; Coburn RF, Ploegmakers F, Gondrie P, Abboud R. Am J Physiol 224: 870–876, 1973). Results include normal values of EV CO contents of resting skeletal muscle and heart ventricular muscle, effects of increasing COHb% saturation and a calculated mean tissue P CO on skeletal muscle EV CO binding, and effects of tissue hypoxia evoked by arterial hypoxemia on EV CO binding in both of these tissues. This study is the first that shows that tissue hypoxia-induced CO shifts out of blood resulting in increased EV CO binding are a mechanism that causes CO toxicity. Projections of results to tissue P CO levels occurring during different severe CO toxicity scenarios predict that skeletal muscle EV CO contents could increase as much as 100 to 300 fold. NEW & NEWSWORTHY This article provides quantification of some physiological parameters that determine carbon monoxide (CO) binding to skeletal and heart muscle extravascular tissue hemoproteins during normal and CO poisoning conditions. This is important information because toxicity occurring during CO poisoning is determined in part by CO binding to these proteins that results in detrimental changes in cellular metabolism.