Quantitation of oxygen consumption and spontaneous muscular activity of the rat

¹ Department of Physiology, St. Louis University School of Medicine, St. Louis, Missouri

Oxygen consumption (Vo₂) and spontaneous muscular activity of albino rats, recorded with apparatus previously described and quantitated with a new technique, exhibited highly significant correlations when paired in successive 10-min periods with a 5-min lag of Vo₂ (y) in respect to spontaneous muscular activity (x). Since fasting and nonfasting male rats of different weights (range: 156–462 g) showed at perfect rest a quite narrow scatter of metabolic rates (y = aKg^b ± 6% se) and since y was linearly correlated with x (se = 7.1% fasting; 5.5% nonfasting), theoretical Vo₂ values could be predicted from y = Kg^b (m + nx) when the appropriate value of b, experimentally found (in this case 0.48), was used. In two-thirds of the observations the lowest 5-min values of Vo₂ did not represent the true basal metabolic rate of the animal since they coincided with variable amounts of spontaneous activity. Data show that the basal metabolic rate of the albino rat is more predictable than generally admitted.