Fig. 3.

Characterization of P-gp transfer. (a) Transferred P-gp is functional, as judged by the change in the Rhodamine 123 extrusion in coculture (gray line) versus BE (2)-C (rightmost black solid line showing concentration without mixing for reference) and BE (2)-CHC(0.2) (leftmost dotted line) cell lines (Left) and the same experiment in the presence of verapamil (Right). In Left, the most resistant subset has a very low peak of rhodamine, but even the most sensitive subset in the mixture shows a peak that has a definite shift toward less rhodamine retention, which is consistent with functioning P-gp transfer. The effect is virtually abolished by verapamil. (b) The extent of P-gp transfer depends on the relative proportions [sensitive/resistant ratio (S/R):80/20; 50/50; 20/80 ratios of BE (2)-C and BE (2)-C/CHC(10′) lines] and levels of P-gp expression in the resistant line [BE (2)-C/CHC(10′) less resistant versus BE (2)-C/CHC(0.2) more resistant]. The peak MDR expression in the AqMDR peak is higher when sensitive cells are incubated with more resistant cells, showing a kind of dose effect. The controls for these experiments are in Fig. 11.