Evaluation of ba1112 rhabdomyosarcoma oxygenation with microelectrodes, optical spectrophotometry, radiosensitivity, and magnetic resonance spectroscopy

We studied tumor tissue oxygenation in the BA1112 rhabdomyosarcoma using microelectrode pO₂ measurements, optical spectrophotometry, analyses of cell survival after irradiation, and ³¹P magnetic resonance spectroscopy (MRS). Studies were carried out in WAG/Rij/Y rats breathing normoxic, hypoxic, and hyperoxic gas mixtures with and without iv administration of perfluorochemical. Significant changes in tissue oxygenation and metabolic status were found when pO₂ values, optical measurements of hemoglobin saturation and cytochrome a, a₃ reduction-oxidation, radiation cell survival determinations, and MRS measurements of phosphometabolite ratios were obtained in rats breathing different gas mixtures. Inhalation of 100% O₂ caused increases in tumor pO₂, hemoglobin saturation, cytochrome a, a₃ oxidation, tumor radiosensitivity, and PCr/P(i), NTP/P(i), and PDE/P(i) ratios. Such changes were augmented by pretreatment with iv perfluorochemicals. Inhalation of hypoxic gas mixtures resulted in reductions in the above parameters. These results indicate that tissue oxygenation can be manipulated reproducibly in the BA1112 rhabdomyosarcoma and suggest that ³¹P MRS can be used to monitor changes in tumor oxygenation in this model system.