An evaluation of the effects of culture medium osmolality and pH on metabolic cooperation between Chinese hamster V79 cells.

The Chinese hamster V79 cell metabolic cooperation assay indirectly measures an inhibition of intercellular communication through gap junctions and can detect many tumor promoters. The experiments described here were designed to determine whether culture medium osmolality and pH affect the endpoint of this assay, since hypertonic solutions and cytoplasmic acidification can uncouple gap junctions in other systems. Hypertonic concentrations of sucrose and mannitol in medium did inhibit metabolic cooperation, but these solutes were active over different ranges of osmolalities. In similar experiments, sodium chloride, choline chloride and sodium glucuronate had no effect on metabolic cooperation. Furthermore, data were obtained indicating that osmotic effects are not likely to contribute to the inhibition of metabolic cooperation by sodium saccharin. It is concluded that hypertonic culture conditions do not necessarily cause an inhibition of metabolic cooperation, and the properties of an added solute are important in determining the effects observed. Additionally, it was found that buffering the culture medium pH between approximately 6.6 and 7.7, during the period when test substances are normally present, had no effect on metabolic cooperation.