The control of some oxidative pathways in guinea-pig mammary-gland mitochondria

Abstract

Methods for the preparation and criteria for the integrity of guinea pig mammary-gland mitochondria are described, and the oxidation of a number of substrates is compared with that of liver mitochondria. Oxidations of the citric acid cycle proceed at approximately the same rate in liver and mammary-gland mitochondria. However, whereas liver mitochondria respire on addition of oxaloacetate, mammary-gland mitochondria do not; they are apparently unable to decarboxylate oxaloacetate at a sufficient rate. The glutamic -dehydrogenase activity of mammary-gland mitochondria is also negligible compared with the high activity of liver mitochondria. The control of the metabolism of glutamic acid by liver and mammary-gland mitochondria presents a number of special and interesting features. The mammary gland appears to have control mechanisms which favor its synthetic activity by preserving metabolites and energy. These are discussed in the light of current ideas on the primitive control of metabolism.