Influence of Carbon Dioxide on Electrophysiology and Ionic Permeability of the Basolateral Membrane of Frog Skin (Epithelia, Ionic Flux, Cellular Ph)
Stoddard, James Stewart
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https://hdl.handle.net/2142/71435
Description
Title
Influence of Carbon Dioxide on Electrophysiology and Ionic Permeability of the Basolateral Membrane of Frog Skin (Epithelia, Ionic Flux, Cellular Ph)
Author(s)
Stoddard, James Stewart
Issue Date
1984
Department of Study
Physiology and Biophysics
Discipline
Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Abstract
When short-circuited epithelia of frog skin bathed in an alkaline Ringer solution equilibrated with room air, are exposed to a Ringer solution equilibrated with 5% CO(,2), inhibition of transepithelial Na('+) transport is observed accompanied by a marked depolarization of the basolateral membrane voltage as measured with intracellular microelectrodes. To study further the mechanisms involved, basolateral membrane influxes and effluxes of ('24)Na, ('42)K, and ('36)Cl were measured in control and CO(,2)-treated isolated epithelia. In control epithelia, studies of the bidirectional ('24)Na fluxes confirmed the existence of an important basolateral membrane permeability to Na('+). The data were supportive of the idea that a significant Na('+) recycling exists at the basolateral membranes of the cells that contributes to the Na('+) load on the pump and participates in the regulation of the Na('+) concentration of the Na('+) transport pool of these epithelial cells. In control epithelia, the apical membranes of the cells were found to be virtually impermeable to Cl('-), while basolateral membranes were highly permeable to Cl('-). The mechanism(s) of basolateral membrane Cl('-) transport appeared to be electroneutral, furosemide and SITS sensitive, and for the most part at least not coupled to the fluxes of Na('+) and K('+). Although CO(,2) caused a partial inhibition of pump activity as assessed from decreases of pump-mediated Na('+) efflux and K('+) influx, CO(,2) caused little or no change of the leak influx of Na('+) or K('+). K('+) efflux was increased markedly with CO(,2) resulting in a net loss of K('+) from the cells. Cl('-) influx was increased and Cl('-) efflux was decreased by CO(,2) leading to a net influx of Cl('-). Although the explicit mechanism(s) by which elevated solution CO(,2) causes a depolarization of basolateral membrane voltage remains unknown, analysis of the data according to criteria involving changes of flux, ionic equilibrium potentials, mass and charge balance restrictions indicated that the principle changes involve a transient decrease in electrical conductance to K('+) with a concurrent increase in electrical conductance to HCO(,3)('-) (OH('-) or H('+)) of the basolateral membranes of the cells. Lastly, a Cl-HCO(,3) exchange mechanism exists at the basolateral membranes of the cells which can markedly affect changes in intracellular pH.
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