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Tumor 31 P NMR p H measurements in vivo : A comparison of inorganic phosphate and intracellular 2‐deoxyglucose‐6‐phosphate as pH nmr indicators in murine radiation‐induced fibrosarcoma‐1
Author(s) -
Soto Gabriel E.,
Zhu Zehua,
Evelhoch Jeffrey L.,
Ackerman Joseph J. H.
Publication year - 1996
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910360508
Subject(s) - fibrosarcoma , intracellular , intracellular ph , extracellular , in vivo , chemistry , phosphate , inorganic phosphate , deoxyglucose , pi , in vitro , biophysics , biochemistry , medicine , pathology , biology , microbiology and biotechnology
Abstract Uncertainty regarding the intracellular/extracellular distribution of inorganic phosphate ( P i ) in tumors has raised concerns that pH calculated from the tumor P i chemical shift may not accurately represent the intracellular pH (pH in ). This issue was addressed in subcutaneously transplanted murine radiation induced fibrosarcoma‐1 by directly comparing pH measured via P i with pH measured via the in situ generated intracellular xenometabolite 2‐deoxyglucose‐6‐phosphate (2DG6P). In 131 comparative measurements employing eight tumor‐bearing mice under both control and hyperglycemic conditions (the latter to extend the range of tumor pH examined), the pH as derived from either 2DG6P or P i showed only a small, but statistically significant, difference (0.07 ± 0.11 SD; P = 0.0001). Scatter in the comparative analysis over the pH range examined ( ca. 5.5‐7.5) was not uniform. Above pH 6.6, 2DG6P indicated a pH lower than that of P i by 0.088 ± 0.105 SD ( n = 107, P = 0.0001); below pH 6.6, 2DG6P indicated a pH essentially identical to and not statistically different from that of P i (mean difference 0.003 ± 0.128 SD ( n = 24, P = 0.92)). Evidence is presented in support of this differential arising from a systematic measurement error due to peak overlap between 2DG6P and endogenous phosphomonoester species. These results support the use of P i as a tumor 31 P NMR pH in indicator, at least in RIF‐1 tumors under control and hyperglycemic conditions.