Evidence that hepatic mitochondrial mass decreases during the first sixteen hours following birth in starved newborn rats

Mitochondrial structure and function in the untreated Jackson toxic milk (tx-j) mouse, a model for Wilson disease

Structural changes in hepatocellular mitochondria are characteristic of Wilson disease (WD). Features include variability in size and shape, increased density of matrix, discreet inclusions, and cystic dilatation of the cristae. We examined the functional basis for these mitochondrial changes in the toxic milk (tx-j) mouse model for WD. Its normal syngeic strain, C3H, served as control. Hepatic histology was near-normal in tx-j mice at 3-4-months-old and showed mild inflammation and steatosis at 6-months-old. Transmission electron microscopy showed typical mitochondrial abnormalities, specifically cystic dilatation of tips of cristae, in 3, 4, and 6-month-old tx-j mice and none in normal 3-month-old C3H mice. Citrate synthase (CS) activity was initially lower in tx-j mice than age-matched controls but increased over the first 6 months such that it was significantly greater at 5 and 6-months-old (p<0.003). No evidence for hepatic mtDNA depletion was found by long-PCR analysis. NB-PAGE showed preservation of all complexes in the oxidative-phosphorylation chain except complex IV which declined markedly from 5-months-old onwards. Hepatic complex IV activity was significantly decreased in 5-month-old tx-j mice (p<0.04). Expression of mitochondrial transfer factor A (TFAM) mRNA declined progressively in 6-8-month-old tx-j mice; immunodetectable protein levels declined in parallel. Expression of mtSSB mRNA was uniformly low in tx-j mice from 1-8-months-old. Levels of two mitochondrial antioxidant proteins capable of binding copper, thioredoxin-2 and peroxiredoxin-3, rose over the first 6 months of life. Mitochondrial changes occur early in WD and reflect complex, probably oxidative, injury.

Evidence that the development of hepatic fatty acid oxidation at birth in the rat is concomitant with an increased intramitochondrial CoA concentration

The development of hepatic fatty acid oxidation during the perinatal period in the rat was studied using isolated mitochondria. Ketone body synthesis from substrates entering at different levels of beta-oxidation was 2-3 times lower in mitochondria isolated from term-fetal liver than in 16-h-old newborn or adult liver mitochondria. The low rate of palmitoyl-L-carnitine oxidation in term-fetal mitochondria was linked neither to the low capacity of the respiratory chain nor to the removal of acetyl-CoA in the hydroxymethylglutaryl-CoA synthase pathway. The 2.5-times lower concentration of CoA found in term-fetal liver mitochondria when compared to 16-h-old or adult liver mitochondria might be the factor responsible for the low rate of fatty acid oxidation in term-fetal liver mitochondria.