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  • Title: Na+-K+ pump stoichiometry and basolateral membrane permeability of frog corneal epithelium.
    Author: Candia OA, Cook P.
    Journal: Am J Physiol; 1986 May; 250(5 Pt 2):F850-9. PubMed ID: 2422959.
    Abstract:
    The Na+-K+ pump flux ratio and the Na+ and K+ permeability of the basolateral membrane of the isolated frog corneal epithelium were studied with the aid of microelectrodes by analyzing the effects of ouabain, Ba2+, and amphotericin B. The experiments were done in Cl(-)-free solutions, a situation that approximates that of static head. Ouabain produced a quick depolarization of the potential difference across the basolateral membrane (PDb) from -72 to -62 mV without a change in resistance. Ba2+ (3 mM) rapidly lowered PDb from -74 to -57 mV and decreased the apical-to-basolateral resistance ratio. The effects of ouabain and Ba2+ were additive. The Na+-K+ flux ratio at the pump was calculated to be 1.78, substantially less than when the tissue is in a level flow condition, suggesting a variable stoichiometry. The K+ and Na+ resistances of the basolateral membrane were 15.7 and 5.5 k omega X cm2, respectively, allowing K+ and Na+ currents that approximately matched those produced by the Na+-K+ pump. The resistance of the basolateral membrane (4.0 k omega X cm2) was double that reported in Cl(-)-rich solutions, suggesting that Cl- contributes to the conductance of this membrane.
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