Wu G, Hamill O P
Section of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853.
Pflugers Arch. 1992 Feb;420(2):227-9. doi: 10.1007/BF00374996.
NPPB (5-nitro-2-(3-phenylpropylamino)-benzoate), a member of the novel class of Cl- channel blockers related to diphenylamine-2-carboxylate, was studied for its effect on the Ca(++)-activated Cl- current (ICl(Ca)) in frog (Xenopus laevis) oocytes. ICl(Ca) was activated by bath application of 5 mM Ca++ to oocytes that had been Ca++ permeabilized with the Ca++ ionophore A23187. In order to prevent the inactivation of ICl(Ca) that occurs with repetitive applications of Ca++, oocytes were also treated with H-7 (1,5-isoquinolinesulfonyl-1,2 methylpiperazine), an inhibitor of protein kinases. NPPB reversibly blocked both the fast transient (Ifast) and slow (Islow) components of ICl(Ca) with inhibition constants of 22 microM and 68 microM, respectively. NPPB block of ICl(Ca) was voltage dependent and potentiated by depolarization of the oocyte membrane. Our results indicate that NPPB is a potent blocker of the oocyte endogenous ICl(Ca), and may prove useful in the study of exogenously expressed Cl channels.
5-硝基-2-（3-苯丙基氨基）苯甲酸酯（NPPB）是一类与二苯胺-2-羧酸盐相关的新型氯离子通道阻滞剂，本研究观察了其对蛙（非洲爪蟾）卵母细胞中钙激活氯离子电流（ICl(Ca)）的作用。通过向已用钙离子载体A23187使钙离子通透的卵母细胞浴槽中加入5 mM钙离子来激活ICl(Ca)。为防止因重复加入钙离子而导致的ICl(Ca)失活，卵母细胞还用蛋白激酶抑制剂H-7（1,5-异喹啉磺酰基-1,2-甲基哌嗪）进行了处理。NPPB可逆性阻断ICl(Ca)的快速瞬态成分（Ifast）和慢速成分（Islow），抑制常数分别为22 microM和68 microM。NPPB对ICl(Ca)的阻断具有电压依赖性，且卵母细胞膜去极化可增强这种阻断作用。我们的结果表明，NPPB是卵母细胞内源性ICl(Ca)的有效阻滞剂，可能在外源表达氯离子通道的研究中有用。
