Abstract
The flow of electrons from substrates through the mitochondria respiratory chain to cytochrome aa3 (Cyt aa3) and O2 provides the energy for ATP production by oxidative phosphorylation (OXPHOS). Bilirubin by uncoupling OXPHOS interfers with this process. This should result in an increased flow of electrons and therefore a tendency for Cyt aa3 to become more reduced. A near-infrared, multiwavelength, differential spectrophotometer was used to test whether hyperbilirubinemia alone or in association with hyperosmolar opening (HOSMO) of blood brain barrier (BBB) can affect the redox state of Cyt aa3. Eight anaesthetized rats, m.wt = 229 g were studied. Following achievement of a steady state of 30% inspired O2 the rats received an IV infusion of bilirubin, dissolved in 0.1 N NaOH, 4% albumin in 1 M PO4 buffer sol., calculated to reach a Se. bili.conc. of 30 mg/dl. Hyperbilirubinemia alone caused a slight or no reduction in Cyt aa3 oxygenated lib (HbO2) or blood volume (BV), However, in combination with HOSMO of BBB with IV infusion of 1.6M arabinose sol., there was a significant reduction of Cyt aa3, 26–47% of total labile signal, smaller changes in HbO2 and an increase in BV. A second dose of arabinose caused an exaggeration of these changes. Similar studies with 5 newborn piglets yielded similar results. We conclude that changes in the redox state of Cyt aa3 can be developed as an index of bilirubin toxicity. Near-infrared spectroscopy may be used to amplify clinical and biochemical findings and assess the risks of hyperbilirubinemia.
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Wu, P., Jobsis, F. & Sylvia, A. CEREBRAL CHANGES IN CYTOCHROME aa3 AS AN INDICATOR OF BILIRUBIN UNCOUPLING OF OXIDATIVE PHOSPHORYLATION. Pediatr Res 32, 612 (1992). https://doi.org/10.1203/00006450-199211000-00047
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DOI: https://doi.org/10.1203/00006450-199211000-00047