Abstract
Summary
Rate of oxygen consumption and spontaneous muscular activity (SMA) were measured in two series of rats of different body weights, treated with a single sc dose (40 mg/kg body wt) of isoproterenol. Minimal calculated metabolic rate (MCMR: “net” O2 consumption unbiased by SMA) reached, within 1 hr, peaks up to +150% in heavier and 110% in lighter rats, above minimal observed metabolic rate (MOMR: resting metabolism of the animal). After 24 and 48 hr, when isoproterenol-induced cardiac lesions were evident, MOMR had returned to normal. However, episodes of SMA in rats with severe cardiopathy elicited disproportionate increases of oxygen consumption (with MCMR significantly higher than MOMR), suggesting caloric inefficiency of the treated animals.
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