Quantitation of acidosis in neonatal brain tissue using the 31 P NMR resonance peak of phosphoethanolamine

31 P NMR brain spectra were obtained from piglets over a range of mild hypocarbia to severe hypercarbia ( P a CO 2 25 to 198 mm Hg). The chemical shifts of the phosphoethanolamine and inorganic phosphate were used to calculate intracellular brain pH (pH et and pH pi , respectively). Both pH pi and pH et underwent parallel significant decreases during hypercarbia, corresponding to 51 and 53% pH regulation , respectively. We conclude that the chemical shift of the phosphomonoester peak in vivo can be used to measure decreases in intracellular pH in neonatal brain. © 1988 Academic Press, Inc.