Ritonavir (RTV) activated volume-sensitive Cl− current (ICl,swell) under isosmotic conditions; RTV-induced currents outwardly rectified and were blocked by DCPIB. (A) Families of currents (-100 to + 60 mV, 500 ms) in control (Ctrl), after RTV exposure (15 μM, 20 min), and after addition of DCPIB (10 μM, 6 min) in presence of RTV (+DCPIB). (B) I-V relationships from A. (C) Current densities at +60 mV (n = 4; Ctrl vs. RTV, P <0.002; RTV vs. +DCPIB, P <0.002; Ctrl vs. +DCPIB, P = 0.71). (D) Kinetics of activation of ICl,swell by RTV (n = 4).