Centre for Perinatal Brain Protection and Repair, Department of Obstetrics and Gynaecology, University College London, London, UK.
Dev Neurosci. 2011;33(6):505-18. doi: 10.1159/000333850. Epub 2012 Feb 9.
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.
我们评估了新生鼠缺氧缺血性脑损伤后脑内 pH 的分布及其与局部损伤的相关性。出生后 7 天的小鼠注射中性红后，行左侧颈总动脉结扎并暴露于 8%氧气中。对 snap-frozen 脑的切面图像进行采集，根据蓝-绿吸光度比值计算 pH 值。单纯结扎颈总动脉无影响，但与缺氧结合可导致 pH 值迅速出现双相下降，第一个平台出现在 15-30 分钟，第二个平台出现在 60-90 分钟。同侧背侧皮质、海马、纹状体和丘脑受影响最明显。对侧 pH 值最初仅为同侧的 30%，随着时间的延长变得更加酸中毒。与单纯缺氧相比，系统血液分析显示，联合损伤导致血糖（1.3±0.2mM）降低 63%，循环乳酸（17.7±2.9mM）增加 2 倍，CO2 降至 1.9±0.1kPa，pH 值（7.26±0.06）下降。再给氧可使全身变化正常化，并导致脑 pH 值在 4-6 小时出现全面碱性反弹。脑损伤的地形学比较仅与 pH 值变化部分相关，同侧海马损伤最严重，对侧皮质酸性部分幸免。
