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Related Experiment Videos

Apical membrane K conductance in the toad urinary bladder.

L G Palmer

    The Journal of Membrane Biology
    |January 1, 1986
    PubMed
    Summary

    This study reveals a novel voltage-dependent potassium conductance (GK) in toad bladder apical membranes. This GK rectifies, activating at negative potentials and influenced by various ions and hormones.

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    Area of Science:

    • Physiology
    • Membrane Biophysics
    • Renal Physiology

    Background:

    • The toad urinary bladder is a model system for studying epithelial transport.
    • Apical membrane ion channels play critical roles in regulating ion and water balance.

    Purpose of the Study:

    • To characterize the voltage-dependent conductance of the toad urinary bladder apical membrane.
    • To identify the ion selectivity and regulatory factors of this conductance.

    Main Methods:

    • Voltage-clamp analysis of toad urinary bladder epithelial cells.
    • Ion substitution experiments to determine current carriers.
    • Flux measurements to quantify ion movement.
    • Pharmacological manipulation with channel blockers and agonists.

    Main Results:

    • A rectifying conductance (GK) was identified in the apical membrane, activating at hyperpolarizing potentials (Vm = -100 mV).
    • The rectified current was primarily carried by cations, predominantly potassium (K+), moving from cell to mucosa.
    • GK was modulated by divalent cations (Ba2+, Mg2+, Ca2+), pH, quinidine, and hormones like ADH and aldosterone.

    Conclusions:

    • The toad urinary bladder apical membrane possesses a significant voltage-dependent potassium conductance (GK).
    • This GK is a key determinant of apical membrane electrical properties and is subject to hormonal and ionic regulation.

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