Van Cappellen Van Walsum Anne-Marie, Rijpkema Mark, Heerschap Arend, Oeseburg Berend, Nijhuis Jan G, Jongsma Henk W
Department of Obstetrics and Gynecology, University Medical Centre St Radboud, 6500 HB Nijmegen, The Netherlands.
Pediatr Res. 2003 Nov;54(5):747-52. doi: 10.1203/01.PDR.0000088013.00581.BD. Epub 2003 Aug 6.
The purpose of this study was to investigate cerebral energy metabolism and acid-base homeostasis during impaired oxygen supply in fetal sheep. Systemic acid-base balance was correlated with the sequence in changes of cerebral phosphorus metabolite ratios and intracellular pH. Phosphorus magnetic resonance spectra were obtained from the brain of six fetal sheep simultaneously with repeated measurements of fetal arterial oxygen saturation and acid-base balance. Fetal hypoxia was induced by gradually reducing the oxygen supply to the anesthetized pregnant ewe to establish an intended arterial pH of 7.00 or lower. The ratio of phosphocreatine to inorganic phosphate decreased from 1.08 +/- 0.10 (SD) during the control period to 0.77 +/- 0.29 at an arterial pH between 7.20 and 7.25. The inorganic phosphate level became significantly increased at an arterial pH between 7.10 and 7.15 compared with control values. With ongoing arterial acidosis, cerebral intracellular pH decreased linearly with the arterial pH. At an arterial pH of 7.00, cerebral intracellular pH was decreased from 7.18 +/- 0.03 to 6.71 +/- 0.28, and phosphocreatine and nucleoside triphosphates levels were decreased significantly. In fetal sheep brain, cerebral oxidative phosphorylation (ratio of phosphocreatine to inorganic phosphate) is already affected at a mild arterial acidosis. At an arterial pH of 7.00 or lower, nucleoside triphosphates disappeared, which almost inevitably was followed by death in fetal sheep.
本研究的目的是调查胎羊在氧供应受损期间的脑能量代谢和酸碱稳态。全身酸碱平衡与脑磷代谢物比率和细胞内pH值变化的顺序相关。从6只胎羊的大脑中获取磷磁共振波谱，同时重复测量胎羊动脉血氧饱和度和酸碱平衡。通过逐渐减少对麻醉的怀孕母羊的氧气供应来诱导胎羊缺氧，以建立预期的动脉pH值为7.00或更低。磷酸肌酸与无机磷酸盐的比率在对照期从1.08±0.10（标准差）降至动脉pH值在7.20至7.25之间时的0.77±0.29。与对照值相比，在动脉pH值在7.10至7.15之间时，无机磷酸盐水平显著升高。随着动脉酸中毒的持续，脑细胞内pH值随动脉pH值呈线性下降。在动脉pH值为7.00时，脑细胞内pH值从7.18±0.03降至6.71±0.28，磷酸肌酸和核苷三磷酸水平显著降低。在胎羊脑中，轻度动脉酸中毒时脑氧化磷酸化（磷酸肌酸与无机磷酸盐的比率）就已受到影响。在动脉pH值为7.00或更低时，核苷三磷酸消失，这几乎不可避免地会导致胎羊死亡。
