A method for measuring energy metabolism and whole body oxidation in small animals with special reference to experimental metabolism and nutrition

Abstract

A technique is described for measurement of oxidation and energy production rate in vitro in small unrestrained animals. The method consists of a combined system of radiorespirometry and indirect calorimetry in an open air circuit. This makes possible the study of the following parameters: whole body energy production rate, net oxidation of fat, carbohydrates and protein, RQ, specific energy production from exogenous labelled substrates, specific activity of (¹⁴CO₂) in expired air and cumulative oxidation of labelled substrates. The accuracy of this system has been evaluated by various methods such as calibration with high precision gases, the burning of methanol and longitudinal studies in growing and weight-stable rodents. The overall accuracy was found to be approximately ± 2% for parameters related to whole body energy metabolism and better than ± 1% for collection of labelled expired CO₂. This includes methodological and interindividual variations among inbred animals. The system also allows the use of intravenous and intragastric infusion lines during long-term periods without any significant restriction of the rats.

Key Words:

• carbon dioxide production
• energy production
• oxygen uptake
• radiorespirometer
• RQ
• whole body metabolism