"Survival" of mitochondria in vitro: physical and energy parameters.

Isolated mitochondria have been maintained active and coupled for 72 hours at 25 C. Survival (retention of respiratory control) is a function of incubation temperature and dependent upon aeration and substrate. ATP does not entirely substitute for substrate, indicating a need for products of active metabolism other than energy. An improvement in respiratory control is often observed during the first several hours of incubation. Sedimentation and resuspension at 24-hour intervals prolonged survival. As revealed by electron microscopy, mitochondria maintained their basic structure during a 72-hour period at 25 C.Survival is a dynamic, energy-requiring process and must be distinguished from so-called "aging" of organelles at ice temperatures. As a manifestation of partial autonomy, survival may prove useful in assessing aspects of mitochondrial function and the mitochondrial-cellular interrelationship.