MAGNITUDE, ORIGIN, AND IMPLICATIONS OF THE DISCREPANCY BETWEEN BLOOD ETHANOL CONCENTRATIONS OF TAIL VEIN AND ARTERIAL BLOOD OF THE RAT

The rat is widely used as an animal model for experiments involving et hanol, and alcohol concentrations in blood obtained from the tail rout inely are used to monitor ethanol exposure and metabolism. The present study demonstrates that during periods of rising and declining ethano l levels, the alcohol concentrations in tail vein blood lags far behin d that of arterial, jugular, or femoral vein blood. As a result, tail vein ethanol concentrations markedly underestimate the concentration i n arterial blood and rapidly perfused tissue during periods of increas ing body ethanol, whereas the reverse is true as body ethanol declines . This discrepancy, which appeared to result from the low blood perfus ion:tissue water ratio in the tail, disappeared when the tail was heat ed to 37 degrees C. Compared with arterial blood, alcohol measurements performed on tail vein blood yielded a much higher apparent K-m for e thanol clearance and a somewhat lower estimate of ethanol reaching the peripheral circulation. We conclude that, for a variety of studies, a nalyses of arterialized blood from the heated tail should yield a mars accurate and reproducible measure of ethanol exposure and/or metaboli sm than does the conventional collection from the unheated tail.