METHODS FOR MEASUREMENT OF ENERGY-EXPENDITURE AND SUBSTRATE CONCENTRATIONS IN SWIMMING RATS

A measuring system is described for the determination of oxygen consum ption (V-O2) and carbon dioxide production (V-CO2) in swimming rats. V -O2 and V-CO2 were measured by means of an O-2-analyzer (Ametek S3A) a nd a mass spectrometer (Balzers QMG 511), respectively, combined with a gas flow meter. The measurements were made in a 5-1 metabolic chambe r on top of a swimming pool in which a water flow of 0.22 mis was main tained. The rats were fitted with an indwelling catheter with its tip at the entrance of the right atrium for the repeated determination of energy substrate and hormone concentrations, before, during, and after swimming. The inaccuracy of the V-O2, and V-CO2, measurements was 0.1 8% and 0.31% of the reading, respectively; the Imprecision was 2.15% a nd 2.59%. This high accuracy and precision of the system was attained by measuring room air for 20 s after each 100 s of measuring air from the metabolic chamber, and by using demineralized water in the swimmin g pool. V-O2, during steady-state swimming was 1.89 +/- 0.06 mmol/kg . min (ca. 60% V-O2max), indicating moderate exercise. Respiratory quot ient (RQ), during steady-state exercise, was 0.80 +/- 0.01. V-O2, and RQ resulted in rates for carbohydrate and fat utilization of 15.6 +/- 0.8 and 15.1 +/- 0.7 mg/kg . min, respectively.