Pentoxifylline increases RIF-1 tumour pO2 in a manner compatible with its ability to increase relative tumour...

The time course and dose response of 600 mm3 subcutaneous RIF-1 tumours to pentoxifylline was measured in terms of relative tumour perfusion, assayed by 86Rb extraction, and pO2 distribution measured by the Eppendorf histograph. Both perfusion and pO2 distribution were maximally increased by 20 mg/kg pentoxifylline 15 min after administration, perfusion to 141 +/- 15% (2 SE) of control, and median pO2 from 3 to 15 mmHg, with the percentage of values < 2.5 mmHg falling from 44 +/- 8% to 22 +/- 7%. Fifteen minutes after administration the pO2 increases were linearly dose-dependent up to 20 mg/kg. Correlation coefficients for perfusion data with the percentages of low values were, for time course and dose response data respectively, 0.76 and 0.84 for median pO2, 0.84 and 0.97 for percentage < 2.5 mmHg and 0.81 and 0.87 for percentage < 10 mmHg. The data show good correlation between changes in perfusion and pO2 distribution parameters, with better correlation for percentage of low values than for median pO2.