Magnetic resonance spectroscopy was used to study intracellular pH and compounds which contain phosphorus in normal human brain and primary brain tumours non-invasively. In normal subjects (n = 7) intracellular pH (pHi) of the brain was 7.03 +/- 0.02 (mean +/- s.e.m.). The pHi did not vary between superficial (2 cm, majority grey matter) and deep brain (5 cm, majority white matter). The relative concentrations of phosphocreatine (PCr) and phosphomonoesters (PME) to ATP were also constant with depth. The relative concentration of phosphodiesters (PDE) increased from superficial to deep in normal brain. The astrocytomas (n = 7, grade II-IV) were significantly more alkaline (pHi = 7.08 +/- 0.03), and contained more PCr and PME, with respect to ATP, than normal brain at similar depth. The meningiomas (n = 4) were also more alkaline (pHi = 7.19 +/- 0.02) with a raised PME level but reduced PCr. The reduction in meningioma PCr may be due to the significant necrosis (greater than 20%) seen in the surgical biopsies. No significant necrosis was seen in the gliomas. Previous in vitro studies suggest that increased PME may be due to accumulation of phosphoethanolamine (PE), a phospholipid precursor. These results suggest that human primary brain tumours characteristically are more alkaline with increased PME than normal brain.
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