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

The perinatal development of the adenine nucleotide translocation in i solated rat brain mitochondria was studied. For that purpose the conte nt of the adenine nucleotide translocase (ANT), the activity of adenin e nucleotide translocation and the control of the ANT protein over Sta te 3 respiration were estimated. From the newborn to the adult state t here was a 4-fold increase in State 3 respiration which was paralleled by a 3-fold increase in the respiratory control ratio. The capacity o f uncoupled respiration exceeded that of State 3 respiration in all de velopmental stages indicating that the activity of oxidative phosphory lation is influenced by that of ANT and/or ATP synthase. The content o f the ANT protein, measured as bound pmoles of [H-3]atractyloside per mg mitochondrial protein, increased more than 2-fold from birth to adu ltness in the first three postnatal weeks. The size of the exchangeabl e matrix (ATP + ADP)-pool was only sligthly expanded during the same p eriod. 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 contr ol 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 r at brain mitochondria is an essential factor for the development of ox idative phosphorylation capacity in the early postnatal period.