Tissue pH in human kidney transplants during hypothermic ischemia

Ex vivo NMR spectroscopy was used to investigate pH in 67 human kidney tran splants. H-1 and P-31 spectra were recorded at 1.5 T during regular hypothe rmic storage in histidine-tryptophane-alpha-ketoglutarate (HTK) solution. E stimations of cytosolic pH from chemical shift differences between inorgani c phosphate and phosphodiesters and of extracellular pH from the epsilon 1 and delta 2 protons of histidine were based upon systematic titration studi es. The possibility to predict acute tubular necrosis (ATN) by measuring pH was compared to results obtained with peak area ratios of phosphomonoester s (PME) and Pi and of the gamma-phosphorus of nucleoside 5'-triphosphate (g amma-NTP) and Pi. Cytosolic pH was 6.86 +/- 0.10 in kidneys showing immedia te post-transplant function and 6.84 +/- 0.10 in those with ATN. Time-depen dent studies demonstrated a monoexponential pH decay (velocity constant: 0. 14 +/- 0.07 h(-1)). Extracellular pH varied between 7.40 and 7.15. Grafts w ith immediate function showed higher PME/Pi (2.24 +/- 0.57 vs. 1.77 +/- 0.5 0, p < 0.05) and gamma-NTP/Pi (0.33 +/- 0.16 vs. 0.16 +/- 0.08, p < 0.001). Intra- and extracellular pH can be monitored non-invasively during hypothe rmic transplant storage. The pH gradient between both compartments provides quantitative information about the buffer capacity of the preservation med ium. Acidification is not a primary cause of ATN during regular HTK storage . The total nucleotide pool is a determinant of the reversibility of ischem ic injury. (C) 2000 Elsevier Science Inc. All rights reserved.