Direct Demonstration of Instabilities in Oxygen Concentrations within the Extravascular Compartment of an Experimental Tumor

Abstract

To test the hypothesis that temporal variations in microvessel red cell flux cause unstable oxygen levels in tumor interstitium, extravascular oxygenation of R3230Ac mammary tumors grown in skin-fold window chambers was measured using recessed tip polarographic microelectrodes. Red cell fluxes in microvessels surrounding pO₂ measurement locations were measured using fluorescently labeled red cells. Temporal pO₂ instability was observed in all experiments. Median pO₂ was inversely related to radial distance from microvessels. Transient fluctuations above and below 10 mm Hg were consistently seen, except in one experiment near the oxygen diffusion distance limit (140 μm) where pO₂ fluctuations were 2 was 2 that extend from perivascular regions to the maximum oxygen diffusion distance. (Cancer Res 2006; 66(4): 2219-23)