Brown Fat Thermoregulation in Developing Hamsters (Mesocricetus auratus): a GDP-Binding Study

Abstract

The thermogenic capacity of brown fat from neonatal and developing hamsters was investigated. The method used was to measure the capacity of brown fat mitochondria to bind externally added guanosine diphosphate (GDP). This gives an estimate of the number of proton-conducting channels and hence the capacity of heat production in the mitochondria. At an age of 12 days post-partum the GDP-binding capacity is low: 0.14 nmol GDP/mg mitochondrial protein. Thereafter the capacity shows a steady increase up to 0.54 nmol/mg at 20 days. The peak is followed by a slow decrease down to the level of the adult hamster: 0.32 nmol/mg. This pattern of brown fat development is strikingly similar to reports on the development of oxygen consumption measured on whole animals or on the ability to maintain a constant body temperature when the ambient temperature is lowered. The calorigenic response to injected noradrenaline also follows this pattern. It is therefore justified to suggest that brown fat is a major effector of regulative metabolic heat production in the developing hamster.