The effect of environmental temperature on protein and energy changes following burn injury in the rat.

The metabolic response to a standard burn injury in rats (25% of body surface area) was investigated at environmental temperature 20 degrees C and 30 degrees C. With an intake of 15 g diet (20% w/w protein) per day, burned rats at 20 degrees C were found to be in negative energy balance mainly due to increased insensible (evaporative) losses, and they lost weight. Fat was the main endogenous source of energy, although protein was also catabolised from both carcass and pelt. At 30 degrees C, insensible losses of burned rats were still high, but they had lower sensible (mainly radiative) losses leading to a positive energy balance and a gain in weight. This consisted mainly of carcass water, fat and protein. Urine catecholamines were higher in burned rats at 20 degrees C than at 30 degrees C and correlated with heat loss, urine nitrogen and urine 3-methylhistidine, supporting the hypothesis that catecholamines play a central role in mediating the protein and energy changes following burn injury. For the first 4-6 days, urine nitrogen and 3-methylhistidine excretion increased in rats at 30 degrees C, suggesting that this early part of the metabolic response is obligatory. These findings support the use of raised environmental temperatures to reduce the metabolic response to burns.