Cellular oxygen consumption depends on body mass.

Hepatocytes were isolated from nine species of mammal of different body mass (and standard metabolic rate). The cells were incubated under identical conditions and oxygen consumption measured. The rate of oxygen consumption (per unit mass of cells) scaled with body mass with exponent -0.18. In general, there was a 5.5-fold decrease in oxygen consumption rate with a 12,500-fold increase in body mass. The decrease in oxygen consumption rate was not due to an increase in cell volume with increasing body mass but to a decrease in intrinsic metabolic activity of the cells. This novel finding confirms and explains the decrease in oxygen consumption rate measured in tissue slices from larger mammals by H. A. Krebs (Biochim. Biophys. Acta 4: 249-269, 1950) and recently by P. Couture and A. J. Hulbert [Am. J. Physiol. 268 (Regulatory Integrative Comp. Physiol. 37): R641-R650, 1995].