Ion transport by heart mitochondria. Retention and loss of energy coupling in aged heart mitochondria.

Abstract The retention and loss of energy-coupling reactions in isolated beef heart mitochondria have been examined under anaerobic conditions using suspending media chosen to mimic the intracellular milieu. In long-term incubations at 37 °C, a loose coupling develops which can be controlled by adding serum albumin. This lesion closely resembles that produced by addition of free fatty acids which has been described in previous studies. Shorter incubation times produce an increased susceptibility to hydrogen peroxide which is characterized by elevated ATPase activity, increased permeability to monovalent cations, and increased proton ejection on transition from the anaerobic to the aerobic state. This peroxide sensitivity is prevented by chelators such as EGTA and appears to involve a time-dependent release of metal ions. Of the metabolites which are known to increase in concentration in the ischemic heart cell, Na + , P 1 , lactate, and H + all promote swelling of isolated heart mitochondria and contribute to a decline in energy coupling. The relationship of these results to the pathological deterioration of mitochondria in ischemic heart tissue is discussed.