Endogenous Carbon Monoxide Production in Man*

Abstract

Since the late 19th century, carbon (CO) has been known to be present in of normal man and animals. The origin in blood, however, has not been entirely Although it might be assumed that all CO is absorbed from the environment, thors have thought that some, at least, endogenously. The difficulties in de whether blood CO arises endogenously oi been the lack of knowledge of the vari govern CO uptake and loss from the uncertainty of the degree of exogenc sure to CO, and the lack of accurate ar CO analytical methods.In 1894, Grehant (1) monoxide nous and endogenous origin of the gas. In rethe blood cent years, the endogenous formation of CO has of the gas been studied by Sjdstrand and his associates in explained. Sweden (6, 7). the blood These investigators, however, have not measmany au-ured the actual rate at which CO is formed. The is formed instrument 1 used in their experiments to analyzẽ termining CO actually measures the temperature increase r not have during its catalytic combustion. In our hands, it is ables that relatively nonspecific for CO, and it seemed posbody, the sible that some of their findings might have been )us expo-produced by the presence of gases other than CO. id specific Their conclusion that CO is produced in normal man (7) depended on the demonstration of )rmal dog higher CO concentrations in expired than in in-)mbustible spired air. This, however, could be possible in the >), Leoper absence of endogenous CO formation if an unbloed (5) steady state existed between blood CO hemogloin human bin (COHb) and inspired CO concentration; this an exoge-could have occurred if their subjects had been exposed to higher CO concentrations in the environment as long as several hours before the experiments. We have developed an analytical method that appears to be specific for CO and can detect the addition of 0.3 ml of CO to the total adult C 0 2 human CO store by the analysis of a 2-ml blood A B SO R B E R sample (8). We have overcome some of the other criticisms by measuring the increase in blood COHb during extended periods of rebreathing in a closed system. METHODS

Use of alveolar carbon monoxide to measure the effect of ribavirin on red blood cell survival†

“…The vast majority of heme turnover results from RBC destruction; thus, the rate of CO production can be used as a quantitative indicator of RBC turnover rate. Measurements of expired CO provide a convenient means of assessing CO production since this gas is cleared entirely via the lungs [17]. However, breath CO originating from heme metabolism (endogenous CO) must be distinguished from CO of environmental origin (exogenous CO).…”

Crigler-Najjar Syndrome: An Unusual Course with Development of Neurologic Damage at Age Eighteen

“…In 197 1 endogenous carbon monoxide production, which provides an independent estimate of total body heme turnover [22], was measured during a base-line period and during phenobarbital and glutethimide treatment, using a closed rebreathing system. Details of the system used and analytic methods employed have been reported previously [lo].…”

Considerations of the physiological variables that determine the blood carboxyhemoglobin concentration in man.

“…It appears, however, that no previous study has considered the physiological variables that determine [COHb] under conditions where inspired air CO concentrations are in the normal range. It has become apparent in recent years that CO is endogenously produced in normal man as a by-product of hemoglobin catabolism (and probably other hemoproteins as well) and therefore that the body CO stores are influenced by endogenous as well as exogenous CO (5,6). The development of a method of measuring the rate of endogenous CO production (Vco) in man (6) has made it possible to study the relationship of Vco and other variables to [COHb].…”

“…It has become apparent in recent years that CO is endogenously produced in normal man as a by-product of hemoglobin catabolism (and probably other hemoproteins as well) and therefore that the body CO stores are influenced by endogenous as well as exogenous CO (5, 6). The development of a method of measuring the rate of endogenous CO production (Vco) in man (6) has made it possible to study the relationship of Vco and other variables to [COHb]. This is of particular interest since the latter has been used as an index of hemolysis (7).…”