Chemical Enhancement of Viral Transformation in Syrian Hamster Embryo Cells by Gaseous and Volatile Chlorinated Methanes and Ethanes

Abstract

Methods were developed for exposing cells in vitro to gases or vapors of volatilized organic liquids. Compounds were selected for their industrial importance, environmental impact, and suspected role in the etiology of some human cancers. Exposure chambers were designed for easy insertion of dishes of cultured cells and were equipped with inlet and outlet ports for introduction and purging of test gases. A gas delivery system utilizing a mass flow meter was used for the quantitative distribution of test gases into exposure chambers. For volatile compounds, appropriate volumes of cold (4°) liquids in glass Petri dishes were quickly placed into chambers, the system sealed, and the compounds rapidly volatilized at 37°. For exposure, the cells and chambers were placed in an incubator and rocked at a constant rate so that a portion of the cells was always in direct contact with the test gases or vapors. Known sample volumes were removed after various treatment times and test gas concentrations determined by standard gas chromatographic techniques. After exposure, the cells were removed and assayed for viability and increased sensitivity to viral transformation. Under these experimental conditions, the volatile liquids 1,1,1-trichloroethane, dichloromethane, chloroform, 1,2-dichloroethane, and 1,1-dichloroethane significantly enhanced transformation of Syrian hamster embryo cells by SA7 adenovirus, while acetone exerted no effect. The gases chloromethane and vinyl chloride were also active in this test system, while bromomethane, methane, and ethane were inactive. Incorporation of some of these compounds into liquid cell culture medium for cell treatment was either unsuccessful or produced only a weak enhancement response. Methodology is now available to evaluate volatile and gaseous carcinogens or mutagens and can be used to identify their mechanisms of action and the relative hazards of these agents to human health.