MEASUREMENT OF DIFFERENCES IN PO(2) IN RESPONSE TO PERFLUOROCARBON CARBOGEN IN FSA AND NFSA MURINE FIBROSARCOMAS WITH LOW-FREQUENCY ELECTRON-PARAMAGNETIC-RESONANCE OXIMETRY

We have used very low-frequency electron paramagnetic resonance (EPR) oximetry to measure the change in oxygen concentration (Delta pO(2)) d ue to change in breathing atmosphere in FSa and NFSa fibrosarcomas imp lanted in the legs of C3H mice infused with perfluoro-octylbromine (PF OB). Measurements in each tumor were made before and after the adminis tration of the high-density (47% v/v) perfluorocarbon PFOB, perflubron (Alliance pharmaceutical Corporation, San Diego, CA). Measurements in each tumor were also made, after the administration of the PFOB, both before (PFOB/air) and after the administration of carbogen (95% O-2 5% CO2, PFOB/carbogen). Large changes (Delta pO(2)) relative to PFOB/ air oxygenation were seen with the administration of PFOB/carbogen. No significant difference in oxygen concentration was seen between air-b reathing mice with and without PFOB. The mean Delta pO(2) for FSa tumo rs was 13 +/- 6 torr, while the mean for NFSa fibrosarcomas was 28 +/- 7 torr. There were such large intertumor differences that the trend t oward a smaller change in the more hypoxic FSa tumors was not signific ant (P = 0.13). This paper describes a novel method of measuring diffe rences in oxygenation in tumor tissues. The results of such measuremen ts indicate large differences in pO(2) response to different breathing atmospheres in PFOB-infused tumors of similar histology. The intertum or Delta pO(2) differences may correlate with differences in radiation response. (C) 1996 by Radiation Research Society