Unique aspects of human newborn cerebral metabolism evaluated with phosphorus nuclear magnetic resonance spectroscopy

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Abstract
In vivo phosphorus nuclear magnetic resonance spectroscopy (31P NMR) was used to evaluate the pattern of phosphate compounds in seven newborn babies (mean gestational age, 32 weeks; birth weight, 1,430 gm; age, 37 days) with a history of perinatal asphyxia. Spectra were collected in a 1.9 Tesla superconductive magnet with surface coil techniques. The spectra had characteristic peaks for phosphorylated monoesters (PME), inorganic phosphate (Pi), phosphodiesters (PD), phosphocreatine (PCr), and ATP. In contrast to cortical spectra from mature animals, these newborn infant 31P NMR spectra were dominated by a large PME peak and had small PCr, Pi, and PD peaks. Intracellular pH, as measured from the chemical shift of the Pi peak relative to the PCr peak, was 7.1 ± 0.1 (SD). We studied one infant postmortem, and a large PME peak was present in his spectrum. The presence of PME 3 hours after death strongly suggests that it is not a sugar phosphate. In NMR spectroscopy, compounds are identified by their chemical shift relative to a known standard (PCr); the chemical shift of the PME peak was 6.5 ppm, suggesting that it is a mixture of phosphoryl ethanolamine and phosphoryl choline. The PCr/Pi ratio (1.3 ± 0.7) and the PCr/ATP ratio (0.7 ± 0.4) were lower in these babies than in mature animals (greater than 2 and greater than 1.4, respectively); the PME/PD ratio (1.2 ± 0.6), however, was much greater in the infants (mature animals, less than 0.2). These findings suggest that there are unique aspects of human newborn cerebral metabolites and bioenergetic reserve.