Dose response to ethanol-containing liquid diets for use in a murine model for studies of biological effects due to...

Dose-response experiments were performed to establish an optimum concentration of ethanol (EtOH) in liquid diet formulations for use with a murine model (C57B1/6) of potential biological effects attributable to EtOH consumption. An optimum concentration was predetermined to be the highest EtOH concentration consumed by mice without resulting in a loss of body weight. Feeding trials were performed using EtOH concentrations that ranged from 25 to 36% ethanol-derived calories (EDC) during 7-day experiments, or 10 to 30% EDC fed during 21-day experiments. The parameters studied included body weight changes, diet consumptions, daily g EtOH kg-1 body weight, as well as differences in mononuclear cell numbers from the spleen, thymus, and bone marrow. Diet consumptions by the EtOH groups and pair-fed (PF) groups were monitored by weight rather than by volume. During either 7-day or 21-day trials, diet consumptions were lower by groups receiving diets of higher EtOH concentrations; however, daily EtOH intake was maximal by groups fed diets of 25% EDC in all experiments. These mice also gained weight, whereas mice maintained on 30% EDC did not gain weight, and mice maintained on diets of 33 or 36% EDC lost significant body weight. Body weight changes in PF groups were similar to their respective EtOH group. Changes in mononuclear cell numbers of the spleen and thymus paralleled the changes seen in body weights. In the 7-day trials, cell counts declined progressively in groups maintained on diets of high EDC (> or = 30% EDC) or their PF controls. From the 21-day trials, cell counts of both the 30% EDC group and their PF controls declined, compared with all other groups. Together, the conclusion drawn from these findings was that nutritional stress was principally responsible for the mononuclear cell depletions. This contradicts previous reports and highlights the need for strict attention to the pairfeeding paradigm to avoid masking a nutritional component of such studies through overfeeding of the PF controls. Liquid diets of 25% EDC were determined to be optimal for immunological studies using a murine model, because this concentration maximizes EtOH consumption and maintains body weight of the experimental animals.