Postnatal Mitochondrial Differentiation in the Newborn Rat

Postnatal changes in rhodamine‐123 stained mitochondrial populations are sensitive to protein synthesis inhibitors but mimicked in vitro by atp

“…In agreement with this our results show (Table 1) that the RCI increased 2-fold within the first hour of extrauterine life, reaching values very similar to those of adult mitochondria. The rapid postnatal enhancement of the RCI and of the ADP/O ratio to adult values suggests that liver mitochondria attain the oxidative phosphorylation capacity of the adult shortly after birth, in agreement with what has been described previously [1, 3,15,16]. Under the same circumstances, the percentages of mitochondria fluorescence populations changed markedly during the first hour of extrauterine life (Table 2).…”

“…Thus, liver mitochondria attain the functional capacity of adult life within the first hour after birth as shown by the sharp increase in RCI [ 1,151 and the enhancement in the synthesis of mitochondrial oxidative machinery components [3,16]. In agreement with this our results show (Table 1) that the RCI increased 2-fold within the first hour of extrauterine life, reaching values very similar to those of adult mitochondria.…”

“…On the other hand, some evidence supports the hypothesis that protein synthesis is the limiting factor in the acquisition of rnitochondrial function maturity that occurs immediately after birth [3,16]. Actually, there is an important increase in cytochrome and respiratory complex contents in rat liver mitochondria during the first hour after delivery [3,16,24] concurrent with the enhancement in the respiratory parameters observed under these circumstances (Table 1).…”

“…Actually, there is an important increase in cytochrome and respiratory complex contents in rat liver mitochondria during the first hour after delivery [3,16,24] concurrent with the enhancement in the respiratory parameters observed under these circumstances (Table 1). Accordingly, the induction of the synthesis of mitochondrial proteins is triggered immediately after birth [16], coinciding with the rapid postnatal enhancement in the LFPBIFP ratio observed in our experiments (Table 2).…”

“…Actually, there is an important increase in cytochrome and respiratory complex contents in rat liver mitochondria during the first hour after delivery [3,16,24] concurrent with the enhancement in the respiratory parameters observed under these circumstances (Table 1). Accordingly, the induction of the synthesis of mitochondrial proteins is triggered immediately after birth [16], coinciding with the rapid postnatal enhancement in the LFPBIFP ratio observed in our experiments (Table 2). Indeed, protein synthesis is involved in the postnatal changes in mitochondrial populations because the administration of cycloheximide or streptomycin, -inhibitors of cytoplasmic or mitochondrial protein synthesis, respectively-at birth clearly altered the postnatal changes in the mitochondrial LFP/HFP ratio (Tables 2 and 3).…”