Mitochondrial regulation of tissue respiration

¹ Department of Physiology, University of North Carolina Medical School, Chapel Hill, North Carolina

Mitochondrial and nuclear counts and homogenate and washed mitochondrial qO₂ determinations were made on kidney cortex, liver and brain of albino rats. Homogenate qO₂ was inversely related to mitochondrial count in the three tissues, but directly related to cellularity and to O₂ uptake per mitochondrion. It is shown that the former is a spurious and the latter a real correlation. It is concluded that the characteristic differences in the qO₂ of these three tissues are due largely to specific differences in the oxidative metabolism of their respective mitochondria and not to differences in the mitochondrial count per unit weight of tissue.