Background: The purpose of this study was to characterize the estimation of blood alcohol (ethanol) concentration (BAC) in laboratory rats by measuring ethanol concentration in breath (BrAC) using a specialized apparatus in combination with a gas chromatography system.
Methods: The apparatus consisted of a body chamber, a plastic cylinder, from which the head of the rat protruded, a head chamber, and a water-jacketed cylinder, in which the rat's head was placed while the breath sample was collected. The breath sample was withdrawn from the head chamber through a sample loop by a Minipuls pump and then injected directly into the gas chromatography system that was equipped with a flame ionization detector for the quantification of ethanol. For these experiments, Lewis rats were catheterized 1 week before the commencement of the experiments so that blood samples were collected at exactly the same time as the breath samples.
Results: Our results show that Lewis rats can be trained to enter and be secured in the body chamber and that they appear to be comfortable for periods as long as 150 min. The profiles of the pharmacokinetic curves for BrAC and BAC were essentially identical. Cmax for BrAC and BAC at 8 min after the intraperitoneal injection of ethanol was directly proportional to the doses of ethanol. The ratio of BrAC expressed as peak area to BAC (expressed as mM) was calculated to be 3282. This conversion factor can be used to directly estimate the BAC from the BrAC.
Conclusions: The principal conclusion of this study was that the rat breathalyzer is an accurate and convenient laboratory method to estimate BAC in a noninvasive manner. This procedure will be particularly useful for studies requiring repeated assessment of alcohol levels.