Chronic alterations in energy metabolism in the burned rat

Growth rates and food consumption were measured in rats following a non lethal scald burn on 26-28 per cent body surface to develop an animal model for studies of chronic metabolic alterations in the post burn recovery period. The injury was produced by immersing the dorsum of 235-260 g rats in 90°C water for 10 seconds. The burned animals grew at an attenuated rate compared to controls. At 11 weeks post burn, prior to the wound healing of the first rat, the burned animals weighed only 394 ± 10 g v. 494 ± 9 g (mean ± s.e.) in controls. At 42 weeks, when half of the animals healed, the body weight of healed rats (547 ± 16 g) was lower (P<0·05) than that of controls (618 ± 14 g), but greater (P<0·001) than that of their unhealed counterparts (426 ± 13 g). During the period from 42 to 63 weeks the weight of healed rats gradually approached that of controls (P<0·3) while the growth of unhealed animals was virtually arrested. During the first 10 days post burn, food consumption was diminished. However, in the subsequent period food intake per unit of body weight or body surface, which were linearly related for the weight range studied, was elevated in burned rats. At 11 weeks the corrected food consumption of burned animals was elevated 30 per cent (P<0·001). At 42 and 63 weeks, unhealed rats consumed 32 per cent (P<0·001) and 43 per cent (P<0·001) more per unit body weight or surface than corresponding controls. During this later period, the relative food consumption of healed animals became equal to that of controls. The persistently elevated food consumption per unit of body weight or surface suggests the development of hypermetabolism in burned rats. This similarity to burned patients may permit elucidation of factors controlling energy metabolism after thermal injury.