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

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  • Transport Processes, Metabolism and Endocrinology; Kidney, Gastrointestinal Tract, and Exocrine Glands
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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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Authors and Affiliations

  1. Section of Neurobiology and Behavior, Seeley G. Mudd Hall, Cornell University, 14853, Ithaca, NY, USA

    George Wu & Owen P. Hamill

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  1. George Wu
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  2. Owen P. Hamill
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Wu, G., Hamill, O.P. NPPB block of Ca++-activated Cl− currents in Xenopus oocytes. Pflügers Arch. 420, 227–229 (1992). https://doi.org/10.1007/BF00374996

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  • DOI: https://doi.org/10.1007/BF00374996

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