AUTOMATED, 8-CAGE INDIRECT CALORIMETRY IN RATS

We have constructed an automated, eight-cage indirect calorimeter (AIC ) for the measurement of energy expenditure in rats. We compared the m easurements of resting energy expenditure (REE) in rats during a 30-h fast obtained with the AIC with those obtained with a manual indirect calorimetry (MIC) system. There was both a high degree of correlation between the two techniques during the initial 18 h of the fast (r = 0. 90, P < 0.05) and strong intertechnique agreement. REE (AIC) decreased during the final 12 h of the 30-h fast (79.6 +/- 2.7 - 72.0 +/- 4.4 k cal . kg(-0.75) . d(-1) [mean +/- SD, P < 0.01]). REE (MIC) did not sh ow a significant decrease during this part of the fast (79.7 +/- 2.6 - 75.2 +/- 4.7 kcal . kg(-0.75) . d(-1) [P = NS]). During the final 12 h of the fast, agreement between the two systems gradually dissipated and correlation was poor (r = 0.375, P < 0.05). The frequency of anima l handling necessitated by MIC may have resulted in a stress-induced i ncrease in metabolic work that would mask the animals' adaptive respon se to starvation. This investigation demonstrates the advantages of th e AIC and calls into question the accuracy of manual methods under lon g-term starvation conditions. Nutrition 1998;14:672-677. (C) Elsevier Science Inc. 1998.