Studies on rat liver mitochondria: 4. Enzyme activities in mitochondria preserved at 0-4 degrees C

Rat liver mitochondria, stored with the energy-linked functions preserved or in aging conditions, were used to assay the activity of various enzymes during five days. The preservation of energy-linked functions was monitored by the respiratory control coefficient. ATPase, cytochrome oxidase and NADH dehydrogenase showed increased activity when the energy-linked functions were preserved. In aging conditions, cytochrome oxidase, NADH dehydrogenase and ATPase showed decreased activity. The ATPase activity increased only when mitochondria were stored in the presence of inhibitors of the electron transport chain. The activity of NADH oxidase did not change, and succinate oxidase and succinate dehydrogenase showed a small decrease in their activity. The enzymes of the matrix, alpha-ketoglutarate dehydrogenase, malate dehydrogenase and aspartate aminotransferase showed little decrease in activity under either of the conditions of storage. The total protein content decreased slightly under both conditions of storage. These results show that the activity of the enzymes analysed was maintained at reasonable levels, when the energy-linked functions of isolated mitochondria were preserved.