Rapid preparation of subsarcolemmal and interfibrillar mitochondrial subpopulations from cardiac muscle.

1. Subsarcolemmal and interfibrillar mitochondria were prepared with complete recovery from rabbit and porcine heart muscle by upward-flotation during 60 sec of Percoll density gradient centrifugation. 2. Mitochondrial subpopulations were identified and characterized according to buoyant density, electron-microscopy, marker enzyme activities and respiratory performance. 3. ADP-induced state 3-respiration related to latent citrate synthase activity as a marker for structurally intact mitochondria was not significantly different in both mitochondrial subtypes.