Difficulties in Measuring Human Blood Acetaldehyde Concentrations During Ethanol Intoxication

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Abstract
The determination of human blood acetaldehyde (AcH) concentrations is complicated by two artefactual reactions, one resulting in the disappearance of AcH prior to deproteinization of the blood and the other resulting in the formation of AcH during deproteinization. The AcH formation increases with increasing ethanol concentration and decreases with increasing blood dilution, while the rapid AcH disappearance is initiated at the start of the blood collection. The magnitudes of these artefactual reactions are of such an order that a re-evaluation of previous reports on human blood AcH levels is needed. To circumvent these difficulties we suggest that blood should be deproteinized immediately (<5s) after arterial or venous puncture and corrections for AcH formation should be determined under the experimental conditions employed. The first data available on human blood AcH concentrations during ethanol intoxication, determined with such methods (20 to 40 μM AcH after 1 g/kg ethanol), revealed no differences between the estimated in vivo arterial and venous AcH concentrations. One of the reasons for the slow progress in acetaldehyde (ACH) research has surely been the difficulties involved in determining AcH in biological samples. The lack of reliability, specificity and convenience of some older procedures, including colorimetric (Stotz, 1943), spectrophotometric (Burbridge, Hine, and Schick, 1950), radiochemical (Casier and Polet, 1958) and enzymatic (Lundquist, 1958) methods, has been emphasized by Diiritz and Truitt (1964), who introduced head-space gas chromatographic determination of blood AcH. This original head-space method, which involved incubation of denatured blood without removal of precipitated blood proteins, was soon found to be complicated by an ethanol-induced non-enzymatic formation of AcH during the incubation prior to head-space analysis (Truitt, 1970). This method was improved by removal of the proteins from the deproteinized blood samples (Truitt, 1970; Truitt, 1971). However, a non-enzymatic AcH formation has been found even in protein-free, acid supernatants of rat and human blood (Sippel, 1973; Eriksson, Sippel, and Forsander, 1975). Recently it was demonstrated that the major portion of the non-enzymatic AcH formation is not due to the relatively long incubation prior to the head-space analysis, but developes during the deproteinization step (Stowell, Greenway, and Batt, 1977). The problem of the non-enzymatic ally formed AcH has not yet been satisfactorily solved. Thiourea, an effective inhibitor of this reaction in liver and brain supernatants (Sippel, 1972; Eriksson, Sippel, and Forsander, 1977), was first believed to inhibit the reaction also in blood (Sippel, 1972), but later shown to be without effect (Eriksson, Sippel, eind Forsander, 1977). Since it has been indicated that both the ethanol concentration and the blood dilution influences this formation (Eriksson, and Sippel, and Forsander, 1975; Stowell, Greenway, and Batt, 1977), we decided to investigate these relationships in order to develop a correction method for the determination of human blood AcH concentrations during ethanol intoxication. This investigation resulted in the discovery of a new difficulty, namely a rapid disappearance of the AcH in human blood during blood collection.