Brown adipose tissue activity in pyrexial cases of cot death.

Brown adipose tissue was investigated in two cases of cot death in which core temperatures were above 40 degrees C on arrival at the mortuary. Evidence was obtained from mitochondrial (8-3H) guanosine diphosphate (GDP) binding and oxygen uptake of active thermogenesis with uncoupled mitochondrial respiration which was recoupled by GDP. Thermogenic capacity of brown adipose tissue, estimated by radioimmunoassay of the specific mitochondrial membrane "uncoupling protein" responsible for heat production, was similar to that measured in other infants or in experimental animals acclimated to moderately warm conditions (23 degrees C). Brown adipose tissue thermogenesis, occurring inappropriately in a warm, well insulated infant, could be a cause of some cases of cot death.