Deterioration of rat liver mitochondria under conditions of metabolite deprivation

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Abstract
Changes in mitochondrial phospholipid metabolism and energy-linked functions were monitored as coupled mitochondria were aged in iso-osmotic sucrose solution at 18.degree. C. The sequence of events that occur in mitochondrial deterioration under the above conditions were established more completely. Total adenine nucleotides are depleted early in the aging process and their loss parallels the decline in respiratory control. Related to the loss of total adenine nucleotides is a dramatic decrease in ADP and ATP translocation (uptake). The decline of respiratory control is due primarily to a decrease in State-3 respiration; loss of this respiratory activity can be related to the decline in ADP translocation. Mitochondrial ATPase activity does not increase significantly until State-4 respiration has increased appreciably. At the time of loss of respiratory control the ATPase activity increases to equal the uncoupler-stimulated activity. The H+/O ratio and P/O ratios do not decrease appreciably until respiratory control is lost. Similarly, permeability of the membrane to the passive diffusion of protons increases only after respiratory control is lost. There are probably 2-main phases in mitochondrial aging. The 1st phase is characterized by loss of the ability to translocate adenine nucleotides. The 2nd phase is characterized by a decline in the ability of the mitochondrion to conserve energy (i.e., maintain a respiration-driven proton gradient) and to synthesize ATP.