RELATIONSHIP BETWEEN TUMOR OXYGENATION, BIOENERGETIC STATUS AND RADIOBIOLOGICAL HYPOXIA IN AN EXPERIMENTAL-MODEL

Tumour oxygenation and bioenergetic status were measured in the same t umour and these results related to radiobiological hypoxia. A C3H mous e mammary carcinoma grown in the feet of CDF1 mice was used, Bioenerge tic status was assessed by (31)p MRS using a SISCO 7 Tesla magnet, oxy gen measurements were done by a polarographic electrode and the hypoxi c fraction was determined from direct analysis of the radiation dose-r esponse data. During all examinations restrained, non-anaesthetized mi ce were allowed to breathe either 100% oxygen, carbogen, normal air, c arbon monoxide (CO) at 75, 220, or 660 ppm or had blood flow occluded by clamping. Results showed a significant correlation between the radi obiological hypoxic fraction and % pO(2) less than or equal to 5 mmHg under the different treatment conditions, whereas no correlation was f ound between beta nucleosidetriphosphate/inorganic phosphate (beta-NTP /Pi) ratio and either the hypoxic fraction or the % of pO(2) values le ss than or equal to 5 mmHg under the different treatment conditions, I n conclusion, oxygen electrode measurements were sensitive to changes in tumour hypoxia whereas the bioenergetic status alone seemed to be a less precise measure of hypoxia in this tumour model. Furthermore, th e present study demonstrated that tumour cells in vivo can actually ma intain the bioenergetic status during a period of severe hypoxia.