Fig. 3.

The concentration dependence of nizatidine (0.05–10 mM) secretory (BL–AP) transport across Caco-2 cell monolayers in the absence of inhibitors (closed circle) and under complete P-gp inhibition (open circle). The data in the absence of inhibitors were well described by a model consisting of one saturable and one nonsaturable component, as described under the “Data Analysis” section. The conditions for complete P-gp inhibition (1 mM of verapamil) were identified from the lower plateau region of the concentration-dependent inhibitory effect of verapamil on nizatidine BL–AP transport. Each data point represents the mean ± SD of studies across three transwells (n = 3)