Fig. 4.

Effects of EIPA, ouabain, or monensin, alone, or in combination on net MTX levels in R1-11-PCFT-h cells incubated in HBS (pH 7.40) or RPMI (pH 7.3). (A) Net MTX uptake (100 μM) was assessed after 40 minutes with and without EIPA (10 μM), ouabain (10 μM), or monensin (50 μM) added simultaneously with [³H]MTX. Cell MTX is expressed in units of picomoles per milligram protein. (B) Net MTX uptake (100 μM) was assessed after 40 minutes in the presence of monensin (50 μM) with and without EIPA (10 μM), ouabain (10 μM), or FCCP (10 μM) added simultaneously with [³H]MTX. Net MTX uptake in RPMI without any addition was set as 100% as a basis for comparison. Data in both panels are the mean ±S.D. from three independent experiments.