concanavalin-a and 7-methylguanine

1-Methylguanine and 7-methylguanine, both metabolic products of tRNA degradation, are known to induce transformation of Chinese hamster fibroblasts in culture. The effects of these compounds on the cell membrane have been studied by the method of Concanavalin A-mediated hemadsorption. 1-Methylguanine or 7-methylguanine induced a 50% increase of Con A-mediated hemadsorption within 20 hours of exposure of the cells to the agent at a concentration of 10(-5) M. This alteration was reversed within 13 days when the cells were grown in the control medium. Prolonged treatment with 1-methylguanine or 7-methylguanine resulted in changes which were only slowly reversed during growth of the cells in the control medium. The effect of the methylated purines on the cell membrane could be completely inhibited by simultaneous addition of dibutyryl-cAMP at a concentration of 10(-5) M. The possible mechanism of cell membrane alteration by methylated purines and its relevance to transformation in vitro are discussed.

Topics: Agglutination; Animals; Cells, Cultured; Concanavalin A; Cricetinae; Cricetulus; Embryo, Mammalian; Erythrocytes; Guanine; Hemadsorption; Kinetics

Primary Chinese hamster embryo cultures exposed chronically to 1-methylguanine or 7-methylguanine, modified purines derived from nucleic acid turnover, exhibit a number of properties characteristic of transformed cell lines. One of the earliest effects observed following exposure of cells to the methylated purines is an alteration in cell surface properties as measured by the interaction of the cells with the lectin concanavalin A. Within sixteen hours following inclusion of the compounds in the culture medium, the cells exhibit an increase in concanavalin A mediated hemadsorption. The increase in hemadsorption is accompanied by an alteration in distribution of receptors within the cell population as measured by flow microfluorometry using fluorescin conjugated concanavalin A, and by a decrease in the total number of receptors as measured by binding of radiolabelled concanavalin A. Possible mechanisms for these alterations and their significance for growth control are discussed.

Topics: Animals; Cell Membrane; Cell Transformation, Neoplastic; Cells, Cultured; Concanavalin A; Cricetinae; Cricetulus; Cytoskeleton; Flow Cytometry; Guanine; Hemadsorption; Receptors, Mitogen; Surface Properties; Tritium