Fig. 4. Effect of verapamil on CQ-induced changes in the concanamycin-A-induced alkalinisation of the DV in saponin-isolated mature trophozoite-stage CQS and CQR parasites. (A,B) Fluorometer traces showing DV alkalinisation in the absence of CQ and verapamil (black), in the presence of 10 µM CQ (light grey), and in the presence of 10 µM CQ and 50 µM verapamil (red) in the (A) CQS 3D7 strain and the (B) CQR K1 strain. Data are representative of nine independent experiments for 3D7 and four independent experiments for K1. (C) Averaged data obtained from at least three independent experiments (+ s.e.m.) for the CQS 3D7 and D10 strains and the CQR 7G8 and K1 strains. In all cases, CQ and verapamil were added to the parasites 1 minute before the addition of concanamycin A (100 nM).