Effect of DPI on PMA-induced ⁸⁶Rb efflux from human neutrophils. (A) Human neutrophils were loaded with ⁸⁶Rb and pretreated with the indicated concentration of DPI for 3 minutes. ⁸⁶Rb efflux was subsequently initiated with 100 nM PMA. Data are expressed as percentage of the value obtained in the absence of DPI. Error bars represent standard deviation of 4 parallel samples. (B) ⁸⁶Rb release was related to superoxide production detected in the presence of the same DPI concentration. (C) ⁸⁶Rb release was related to the extent of membrane depolarization obtained in the presence of the same DPI concentration.