Effect of reducing agents and oxygen on plating efficiency of some mammalian cells in culture.

Abstract

In previous studies on factors influencing clonal growth in vitro, a gas phase containing 1% O2 , compared with atmospheric O2 (20%), enhanced plating efficiency (PE). To evaluate whether the lowered PE at 20% O2 could be alleviated by reducing agents, cysteine or thioglycolate was added to the plating medium. A low concentration of cysteine·HCI·H2O (1 mg/100 ml) slightly enhanced clonal growth but was toxic at higher concentrations. With 1% O2 and controlled pH, this cytotoxicity was reduced. In a second culture system widely used for quantitative chemical carcinogenesis in vitro, sodium thioglycolate failed to enhance PEa However, in this system, 1% O2 compared with atmospheric O2 significantly increased the PE of control and benzo[a]pyrene-treated hamster embryo cells plated on an irradiated feeder layer. We conclude that the cytotoxicity or clonal growth inhibition produced by atmospheric O2 cannot be alleviated by addition of either reducing agent to the plating medium.