title: Distribution of pH changes in mouse neonatal hypoxic-ischaemic insult.
abstract: We assessed the distribution in brain pH after neonatal hypoxic-ischaemic insult and its correlation with local injury. Postnatal day 7 mice were injected with neutral red and underwent left carotid occlusion and exposure to 8% oxygen. Images captured from the cut surface of snap-frozen brain were used to calculate the pH from the blue-green absorbance ratios. Carotid occlusion alone had no effect, but combined with hypoxia caused rapid, biphasic pH decline, with the first plateau at 15-30 min, and the second at 60-90 min. The ipsilateral dorsal cortex, hippocampus, striatum and thalamus were most affected. Contralateral pH initially showed only 30% of the ipsilateral decline, becoming more acidotic with increasing duration. Systemic blood analysis revealed, compared with hypoxia alone, that combined insult caused a 63% decrease in blood glucose (1.3 ± 0.2 mM), a 2-fold increase in circulating lactate (17.7 ± 2.9 mM), a reduction in CO(2) to 1.9 ± 0.1 kPa and a drop in pH (7.26 ± 0.06). Re-oxygenation resulted in the normalisation of systemic changes, as well as a global alkaline rebound in brain pH at 4-6 h. A topographic comparison of brain injury showed only a partial correlation with pH changes, with the severest injury occurring in the ipsilateral hippocampus and sparing acidic parts of the contralateral cortex.
authors.affiliation: Centre for Perinatal Brain Protection and Repair, Department of Obstetrics and Gynaecology, University College London, London, UK.
authors.forename: Giles S
authors.initials: GS
authors.lastname: Kendall
authors.forename: Mariya
authors.initials: M
authors.lastname: Hristova
authors.forename: Virginia
authors.initials: V
authors.lastname: Zbarsky
authors.forename: Amanda
authors.initials: A
authors.lastname: Clements
authors.forename: Donald M
authors.initials: DM
authors.lastname: Peebles
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Robertson
authors.forename: Gennadij
authors.initials: G
authors.lastname: Raivich
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality; D006863:Hydrogen-Ion Concentration; D020925:Hypoxia-Ischemia, Brain / Q000097:blood* / Q000503:physiopathology*; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL