The CLAMS unit (Columbia Instruments) is an indirect calorimeter that measures O2 consumption and CO2 production along with spontaneous activity (photo beam sensors) and food intake (precision balances) in mice and rats housed in the metabolic chambers. In addition, the temperature of the testing environment can be adjusted within the range of 4~45°C to meet any experimental design. The thermoneutrality (30-33°C) and/or a cold challenge (4~10°C) have been frequently selected to test the metabolic responses.
The measuring period varies from a few hours to weeks, however, an appropriate acclimation time should be evaluated in determination of the baseline metabolism. Animals are transferred into the testing chambers after being single-housed in their home cages for at least a week. The body weight and body composition are measured before the measurement starts and/or right after it ends. Additional body composition tests seem necessary during the measurement when large changes of BW are expected such as testing animals with a cold temperature.
The VO2, VCO2, RER, activities, and food intake (feeding bouts) in each chamber are sequentially recorded by the system. The data are reported in Excel spreadsheet that includes raw data points, hourly average, and averages in day-time, night-time, and 24 hours period of each day. Our final data report includes the following metabolic parameters.
- VO2 and VCO2 (ml/kg/hr and ml/kg. lean body mass/hr)
- Food Intake (g/hr)
- Activities (counts/hr)
- RER (VCO2/VO2)
- Energy expenditure or heat production (kcal/kg/hr)
- Glucose oxidation (g/kg/hr)
- Fat oxidation (g/kg/hr)
- Body composition (BW, lean mass, fat mass and body fluid in g and %)
- Procedures, calculation equations and references
In some cases, allometric scaling exponents of body mass, analysis of covariance (ANCOVA), or percent relative cumulative frequency analysis (PRCF) may also be used in the analysis.