Simultaneous evaluation of the effects of RF hyperthermia on the intra- and extracellular tumor pH

• Published in: Magnetic resonance in medicine 2000-01, Vol.43 (1), p.1-8
• Main Authors: Jayasundar, Rama, Honess, Davina, Hall, Laurance D., Bleehen, Norman M.
• Format: Article
• Language: English
• Subjects: Acid-Base Equilibrium; Animals; Biological and medical sciences; Disease Models, Animal; Extracellular Matrix - metabolism; Female; Fiber Optic Technology; Fibrosarcoma - metabolism; Fibrosarcoma - therapy; hyperthermia; Hyperthermia, Induced - instrumentation; Intracellular Membranes - metabolism; Investigative techniques, diagnostic techniques (general aspects); magnetic resonance; Magnetic Resonance Spectroscopy; Medical sciences; Mice; Mice, Inbred C3H; Miscellaneous. Technology; Radio Waves; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Sensitivity and Specificity; Skin Neoplasms - metabolism; Skin Neoplasms - therapy; tumor
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/(SICI)1522-2594(200001)43:1<1::AID-MRM1>3.0.CO;2-2

31P‐magnetic resonance spectroscopy (MRS) and a fiberoptic pH meter were used simultaneously to follow the changes in intra‐ (pHi) and extracellular pH (pHe), respectively, of murine RIF‐1 tumors with hyperthermia. Hyperthermia was induced at 34 MHz using the same coil used for MR. The study was carried out until 3.5 hr after hyperthermia. In untreated tumors (n = 29), pHi was always higher than pHe. pHi was reduced after hyperthermia (30 min) at both 42°C and 45°C. pHe registered an increase after 42°C and a decrease after 45°C. The reduction in pHi was larger than the initial differential between pHi and pHe, and the change in pHe was relatively small. Hyperthermia changed the acidity of the intra‐ and extracellular compartments, such that pHe became more alkaline than pHi by 0.15 ± 0.13 units after 42°C [pHe (7.20 ± 0.12) and pHi (7.03 ± 0.05)], and by 0.12 ± 0.14 units after 45°C [pHe (6.84 ± 0.24) and pHi (6.72 ± 0.19)]. Simultaneous measurements of pH from the intra‐ and extracellular compartments demonstrated reversal in the pH gradient after hyperthermic treatment. Magn Reson Med 43:1–8, 2000. © 2000 Wiley‐Liss, Inc.