Fatty acid oxidation by mitochondria from cold-fasted rats

¹ Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts

Mitochondria from ‘cold-fasted’ rats oxidized about as much acetate-1-C¹⁴ to C¹⁴O₂ as did mitochondria from control rats when the data were expressed on the basis of dry weight of the mitochondria. This was a most surprising result because liver slices (wet weight basis) and liver homogenates (protein content basis) from cold-fasted rats form far less C¹⁴O₂ from acetate-1-C¹⁴ than do similar preparations from control rats. The possible reasons for these differences in results with liver slices and liver homogenates on the one hand and liver mitochondria on the other are discussed. Mitochondria from cold-fasted rats were also found to oxidize palmitate-1-C¹⁴ to C¹⁴O₂ as rapidly as the mitochondria from control rats, thereby confirming the results obtained with liver slices. Carbohydrate metabolism failed to promote palmitate oxidation by mitochondria from cold-fasted rats; just the opposite result is obtained with liver slices. The use of mitochondria to study the regulation of multistep metabolic pathways is discussed.