EFFECT OF ACUTE EXERCISE ON AMINO ACID INCORPORATION INTO MITOCHONDRIA OF RABBIT TISSUES

Rabbits were subjected to periods of acute swimming exercise. Mitochondria isolated from the heart and brain of these animals showed an increased in vitro incorporation of [14C]leucine into the mitochondrial protein. However liver mitocondria showed no change. The increased leucine incorporation in heart mitochondria was critically dependent on the concentration of ATP and the buffer employed in the assay system; maximal incorporation occurred at 1.5 mM ATP in the presence of an ATP-regenerating system and Bicine (N,N-bis-(2-hydroxyethyl)glycine) buffer. When ATP concentration was increased further, the mitochondria from the swimming group showed no greater incorporation than the controls. Tris and other buffers depressed leucine incorporation. Addition of proline was required for maximal incorporation, and NH4+ produced a striking but transitory stimulation of leucine incorporation. After the swimming period, the heart mitochondria separated into two peaks after equilibrium centrifugation in a sucrose density gradient: such an effect could also be produced by aging of normal heart mitochondria. © 1969.