Abstract
Using 1H and 31P magnetic resonance spectroscopy (MRS) we aimed to investigate relationships between 1H spin-spin relaxation times (T2s) and nucleotide triphosphate (NTP; largely ATP) levels in newborn piglet brains after acute hypoxia-ischaemia. Six newborn piglets had bilateral common-carotid occlusion and hypoxaemia for ≤ 1.5 hr followed by reperfusion and normal oxygenation. NTP levels were defined relative to the exchangeable 31P pool (EPP = inorganic phosphate + phosphocreatine (PCr) + (γ + α + β)-NTP). Control T2s (mean (SD)) of choline (Cho), creatine + PCr (Cr), and N-acetylaspartate (Naa) were 255 (50), 160 (23), and 215 (34) ms respectively; NTP/EPP was 0.21 (.01). During the insult, Cr T2 rose to 263 (51) ms (p<.0002; paired t-test) as NTP/EPP fell to 0.05 (.05) (p<.0005). An hour after resuscitation, both NTP/EPP and Cr T2 reverted to control values. In 3 piglets, studies continued for up to 50 hr. NTP/EPP fell as secondary energy failure (SEF) developed and the Cho, Cr, and Naa T2s rose linearly to 520 (p<.02), 620 (p<.001), and 590 (p<.001) ms respectively. The increased T2s during the development of SEF were probably due to failure of the ATP-dependcnt Na+/K+ pump indicating their value as indices of cellular oedema following birth asphyxia.
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