Properties of sodium pumps in internally perfused barnacle muscle fibers

M. T. Nelson, M. P. Blaustein

    Research output: Contribution to journalArticlepeer-review

    Abstract

    To study the properties of the Na extrusion mechanism, giant muscle fibers from barnacle (Balanus nubilus) were internally perfused with solutions containing tracer 22Na. In fibers perfused with solutions containing adenosine 5'-triphosphate (ATP) and 30 mM Na, the Na efflux into 10 mM K seawater was ~ 25-30 pmol/cm2/s; 70% of this efflux was blocked by 50-100 μM ouabain, and ~ 30% was blocked by removal of external K. The ouabain-sensitive and K-dependent Na effluxes were abolished by depletion of internal ATP and were sigmoid-shaped functions of the internal Na concentration ([Na]i), with half-maxima at [Na]i ≃ 20 mM. These sigmoid functions fit the Hill equation with Hill coefficients of ~ 3.5. Ouabain depolarized ATP-fueled fibers by 1.5-2 mM ([Na]i ≥ 30 mM) but had very little effect on the membrane potential of ATP-depleted fibers; ATP depletion itself caused a 2-2.5 mV depolarization. When fueled fibers were treated with 3,4-diaminopyridine or Ba2+ (to reduce the K conductance and increase membrane resistance), application of ouabain produced a 4-5 mV depolarization. These results indicate that an electrogenic, ATP-dependent Na-K exchange pump is functional in internally perfused fibers; the internal perfusion technique provides a convenient method for performing transport studies that require good intracellular solute control.
    Original languageEnglish
    Pages (from-to)183-206
    Number of pages23
    JournalJournal of General Physiology
    Volume75
    Issue number2
    Publication statusPublished - 1980

    Keywords

    • pharmacology: Adenosine Triphosphate
    • Animals
    • drug effects: Biological Transport, Active
    • Dose-Response Relationship, Drug
    • drug effects: Membrane Potentials
    • metabolism: Muscles
    • pharmacology: Ouabain
    • Perfusion
    • pharmacology: Potassium
    • metabolism: Sodium
    • metabolism: Thoracica

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