PRACTICAL ASPECTS OF INDIRECT CALORIMETRY IN LABORATORY-ANIMALS

Oxidation of the energetic subtrates by the body is associated with ox ygen consumption, carbon dioxide production, and heat release specific to the nature of the energetic substrates being oxidized. Therefore, measurement of respiratory exchanges (indirect calorimetry) is a power ful method to investigate heat production of a living organism. In thi s article, we review the elementary principles of indirect calorimetry and describe the operating principle of the two most typical devices used to perform indirect measurements of energy expenditure in the lab oratory animal: the closed-circuit and the open-circuit. We then discu ss some practical aspects of the day-to-day use of these devices: resp ective advantages and limitations of each technique, data processing, calibration, correction for body-size, and computation of the energy e xpended for activity. In the second part, we review some of the standa rd formulas of indirect calorimetry that offer the possibility to obta in more precise information such as the rate of oxidation of carbohydr ates (CHO), lipids and proteins if some hypotheses are made on the int ensity of lipogenic, ketogenic, and gluconeogenic processes. Finally, a practical example of the measurement of energetic cost of activity a nd thermic effect of food in the rat is given.