Fischer 344 rats with R3230 Ac mammary
carcinomas implanted in dorsal flap window chambers served as a model to obtain measurements of perivascular and stromal
oxygen tension in normal and
tumor tissues using Whalen recessed-tip
microelectrodes (3- to 6-microns tip). Perivascular measurements were made adjacent to vessels with continuous blood flow. Thus the measurements and models provided are reflective of conditions leading to chronic
hypoxia. Perivascular
oxygen tensions averaged 72 +/- 13 mmHg in normal tissue vessels adjacent to
tumor, 26 +/- 5 mmHg in
tumor periphery, and 12 +/- 3 mmHg in
tumor central vessels. There was a significant trend toward lower perivascular
oxygen tensions in the
tumor center (Kruskal-Wallis test, P = 0.002). A similar tendency was seen with a limited number of stromal measurements. Krogh cylinder models, which incorporate these data for perivascular
oxygen tension, along with morphometric data obtained from the same
tumor model suggest that hypoxic regions will exist between
tumor vessels in the
tumor center unless O2 consumption rates are well below 0.6 ml/100 g/min. The low perivascular measurements observed near the
tumor center combined with the theoretical considerations suggest, for this model at least, that tissue oxygenation may best be improved by increasing red cell velocity and input pO2 and reducing oxygen consumption. The low perivascular
oxygen tensions observed near the center also suggest that conditions conducive to increased red cell rigidity exist, that drugs which can decrease red cell rigidity could improve
tumor blood flow and oxygenation, and that the endothelium of those vessels may be susceptible to
hypoxia-reoxygenation injury.