摘要
To understand more fully the effects of bepridil, an antiarrhythmic and antianginal drug, on myocardial ischemia–reperfusion injury and systemic immune responses, its effect on intracellular Ca2+ levels ([Ca2+]i) in human neutrophils was investigated by using fura-2 as a fluorescent probe. Bepridil (10–200 μM) increased [Ca2+]i in a concentration-dependent fashion. This signal was partly inhibited by removal of extracellular Ca2+. In a Ca2+-free medium, pretreatment with bepridil (100 μM) abolished the Ca2+ release induced by thapsigargin (1 μM), an endoplasmic reticulum Ca2+ pump inhibitor, and by carbonylcyanide m-chlorophenylhydrazone (2 μM), a mitochondrial uncoupler. Pretreatment with carbonylcyanide m-chlorophenylhydrazone and thapsigargin, respectively, partly inhibited bepridil-induced Ca2+ release. Addition of Ca2+ (3 mM) increased [Ca2+]i after pretreatment with bepridil (100 μM) in a Ca2+-free medium. Bepridil (100 μM)-induced Ca2+ release was not altered when phospholipase C was inhibited by U73122 (2 μM). Both Ca2+ release and Ca2+ entry induced by bepridil (100 μM) were augmented by activating protein kinase C with phorbol 12-myristate 13-acetate (10 nM), and were suppressed by inhibiting protein kinase C with GF 109203X (2 μM). Treatment with bepridil (10–20 μM) for 30 min increased the production of reactive oxygen intermediates (ROI) by more than 50%. Collectively, it was found that bepridil increased [Ca2+]i concentration-dependently in human neutrophils by releasing Ca2+ from the endoplasmic reticulum, mitochondria and, possibly, other compartments in a phospholipase C-independent manner. Bepridil also activated Ca2+ influx. The activity of protein kinase C may regulate bepridil-induced Ca2+ release and Ca2+ entry.