An analysis of changes in oxygen tension in stirred cellular suspensions under conditions of radiolytic and cellular consumption.
The determination and maintenance of constant known low levels of oxygen is critical in the study of chemical radiosensitization of mammalian cells in vitro. Both radiosensitization and toxicity effects must be observed, however, in systems were significant consumption of oxygen both by radiation and by cellular metabolism takes place during the experiment. We have analyzed the form of these changes in oxygen tension in stirred cellular suspensions with overlying gas phase under conditions of consumption and found it to conform to the relationship (C[t] - C infinity) = (C[o] - C infinity)e-k1t with C infinity = Cg - R/k1. Here C[t] is the oxygen tension throughout the solution, Cg is the equivalent level in the overlying gas phase, R (concentration units per second) is the depletion rate, and k1 (second-1) is a physical constant independent of oxygen concentration and depletion rate. This relationship has been confirmed in detail using a Clark-type oxygen sensor and a high-stability amplifier design due to Koch with which oxygen levels down to a few hundred parts per million can be determined with accuracy. From these data consumption rates of 4.3 +/- 0.5 ppm O2/rad by radiation in alpha-medium at 27 degrees C, and of (2.9 +/- 1.3) x 10(-17) moles O2/cell/second by metabolizing CHO cells at 37 degrees C have been determined, in agreement with literature values.
D000818:Animals; D002478:Cells, Cultured; D008433:Mathematics; D008954:Models, Biological; D010100:Oxygen / Q000032:analysis; D010101:Oxygen Consumption / Q000528:radiation effects*; D013535:Suspensions; D013997:Time Factors
D013535:Suspensions; D010100:Oxygen