Effects of prolonged hypoxia on the growth and radiation sensitivity of mammalian cells in culture

The purpose of this study was to characterize a model system in which to study hypoxic cell biology in vitro as a function of time under growth and metabolism resulting from prolonged hypoxia affect cellular radiation sensitivity. EMT6/SF cells were grown in monolayers on glass 60 mm petri dishes that had been modified to permit the addition of hypoxic solutions of test drugs or radiolabeled compounds without breaking the system open to air. These dishes were then sealed in aluminum chambers that were evacuated and re-filled eight times with 95% nitrogen/5% carbon dioxide (O2 < 10 ppm). EMT6/SF cells that were maintained at 37 C under hypoxic conditions showed no increase in cell number for up to 70 h. The mitotic index of hypoxic cultures was less than 0.1%, compared to 2.3-3.0% in aerated cultures. The plating efficiency of hypoxic cells decreased with time to 20-30% of control values by 70 h. Aerated cultures consumed glucose more rapidly than hypoxic ones, but, on a per cell basis, hypoxic and aerated cells consumed glucose at equal rates (ca. 1.2 x 10-4 μg/cell/h). Virtually 100% of the glucose consumed was converted into lactic acid in both aerated and hypoxic cultures