Differences in cell surface proteins of drug resistant and sensitive cell lines.

Lactoperoxidase catalyzed iodination of cell surface proteins has been used to compare theophylline and ouabain resistant variants with the drug sensitive parental cell lines. In cells showing contact inhibition a high molecular weight protein was observed to be preferentially labelled. In contrast this was not observed for non contact inhibited cells. These results support a previously suggested correlation between growth regulation and the exposure of this cell surface protein.