Flow Cytometric Studies on Modulation of Cellular Adriamycin Retention by Phenothiazines

Phenothiazines (chlorpromazine and trifluoperazine) enhance the cellular retention and cytotoxicity of Adriamycin in P388/S and P388/R cells. Effects on the resistant cells are more pronounced than those on the sensitive cels. Multiparametric flow-cytometric determination of cellular Adriamycin fluorescence shows that the phenothiazine effects are not uniform in a cell population, and cells in later part of the cell cycle traverse (S and G₂/M), mitogen-stimulated lymphocytes (as compared to nonstimulated lymphocytes), and ascites (as compared to splenocytes) have greater sensitivity to phenothiazine effects on Adriamycin retention.