BIOAVAILABILITY OF ETHANOL IS REDUCED IN SEVERAL COMMONLY USED LIQUID DIETS

Liquid diets are often used as a vehicle for chronically treating laboratory animals with ethanol. However, a recent report suggested that one or more components of these diets may bind ethanol which could result in a decrease in the bioavailability of ethanol. Consequently, we compared the blood ethanol concentration vs. time curves obtained following the intragastric (i.g.) administration of ethanol dissolved in water or in one of three liquid diets (Bioserv AIN-76, Sustacal, or Carnation Slender) using the long-sleep CLS) and short-sleep (SS) mouse lines. The initial rates of absorption were generally the same for the water-ethanol and diet-ethanol groups, but the diets generally produced lower peak levels and the areas under the ethanol concentration-time curves were less for all of the liquid diets than for the control, ethanol-water solution. In vitro dialysis experiments indicated that the Bioserv diet binds ethanol in a saturable manner. Therefore, it may be that the slower release of ethanol, which should occur as a result of binding, serves to increase the role of first pass metabolism in regulating ethanol concentrations following oral administration. Because the effects of the diets were seen even after pyrazole treatment, it may be that the lower blood ethanol levels arise because metabolism by gastric ADH, rather than hepatic ADH, is responsible for a major portion of ethanol metabolism as ethanol is slowly released by the diets. If so, the observation that the diet/water differences were uniformly greater in the LS mice may indicate that LS-SS differences in gastric ADH exist. More generally, the reduced bioavailability of ethanol when given in liquid diets could result in problems especially in those studies that use low concentrations of ethanol.