NPPB block of Ca++-activated Cl- currents in Xenopus oocytes

George Wu; Owen P. Hamill

doi:10.1007/BF00374996

NPPB block of Ca⁺⁺-activated Cl^- currents in Xenopus oocytes

George Wu, Owen P. Hamill

Research output: Contribution to journal › Article › peer-review

40 Scopus citations

Abstract

NPPB (5-nitro-2-(3-phenylpropylamino)-benzoate), a mentoer of the novel class of Cl^- channel blockers related to diphenylamine-2-carboxylate, was studied for its effect on the Ca⁺⁺-activated Cl^- current (I_Cl(Ca)) in frog (Xenopus laevis) oocytes. I_Cl(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 incativation of I_Cl(Ca)) that occurs with repetitive applications of Ca⁺⁺, oocytes were also treated with H-7 (1,5-isoguinolinesulfonyl-1,2 methylpiperazine), an inhibitor of protein kinases. NPPB reversibly blocked both the fast transient (I_fast) and slow (I_slow) components of I_Cl(Ca) with inhibition constants or 22 μM and 68 μM, respectively. NPPB block of I_Cl(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 I_Cl(Ca) and may prove useful in the study of exogenously expressed Cl channels.

Original language	English (US)
Pages (from-to)	227-229
Number of pages	3
Journal	Pflügers Archiv European Journal of Physiology
Volume	420
Issue number	2
DOIs	https://doi.org/10.1007/BF00374996
State	Published - Feb 1 1992
Externally published	Yes

Keywords

Ca-activated Cl current
NPPB
Xenopus oocyte

ASJC Scopus subject areas

Physiology
Clinical Biochemistry
Physiology (medical)

Access to Document

10.1007/BF00374996

Cite this

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title = "NPPB block of Ca++-activated Cl- currents in Xenopus oocytes",

abstract = "NPPB (5-nitro-2-(3-phenylpropylamino)-benzoate), a mentoer 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 incativation of ICl(Ca)) that occurs with repetitive applications of Ca++, oocytes were also treated with H-7 (1,5-isoguinolinesulfonyl-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 or 22 μM and 68 μM, 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.",

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AB - NPPB (5-nitro-2-(3-phenylpropylamino)-benzoate), a mentoer 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 incativation of ICl(Ca)) that occurs with repetitive applications of Ca++, oocytes were also treated with H-7 (1,5-isoguinolinesulfonyl-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 or 22 μM and 68 μM, 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.

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