DEVELOPMENTAL-CHANGES OF THE ADENINE-NUCLEOTIDE TRANSLOCATION IN RAT-BRAIN

The perinatal development of the adenine nucleotide translocation in isolated rat brain mitochondria was studied. For that purpose the content of the adenine nucleotide translocase (ANT), the activity of adenine nucleotide translocation and the control of the ANT protein over State 3 respiration were estimated. From the newborn to the adult state there was a 4-fold increase in State 3 respiration which was paralleled by a 3-fold increase in the respiratory control ratio. The capacity of uncoupled respiration exceeded that of State 3 respiration in all developmental stages indicating that the activity of oxidative phosphorylation is influenced by that of ANT and/or ATP synthase. The content of the ANT protein, measured as bound pmoles of [H-3]atractyloside per mg mitochondrial protein, increased more than 2-fold from birth to adultness in the first three postnatal weeks. The size of the exchangeable matrix (ATP + ADP)-pool was only sligthly expanded during the same period. The translocation activity increased 2-fold from the newborn to the adult state and was a linear function of the ANT protein. Control of the ANT protein over State 3 respiration (quantified as flux control coefficient, C-ANT(Jo)), was remarkable in brain mitochondria from newborn rats (C-ANT(Jo) = 0.45 +/- 0.15), but declined during further development (C-ANT(Jo) = 0.11 +/- 0.03, at the 20th day). The obtained results suggest that the postnatal enrichment of the ANT protein in rat brain mitochondria is an essential factor for the development of oxidative phosphorylation capacity in the early postnatal period.