Cationic selectivity and competition at the sodium entry site in frog skin.

Journal Article (Journal Article)

The cation selectivity of the Na entry mechanism located in the outer membrane of the bullfrog (Rana catesbeiana) skin epithelium was studied. This selectivity was determined by measuring the short-circuit current when all of the external sodium was replaced by another cation and, also, by noting the relative degree of inhibition that the alkali metal cations produced on Na influx. The ability of the Group Ia cations to permeate the apical membrane was determined from the tracer uptake experiments. The results demonstrate that (a) only Li and Na are actively transported through the epithelium; (b) the alkali cations K, Rb, and Cs do not enter the epithelium through the apical border and, therefore, Na and Li are the only alkali cations translocated through this membrane; (c) these impermeable cations are competitive inhibitors of Na entry; (d) the cations NH4 and Tl exhibit more complex behavior but, under well-defined conditions, also inhibit Na entry; and (e) the selectivity of the cation binding site is in the sequence Li congruent to Na > Tl > NH4 congruent to K > Rb > Cs, which corresponds to a high field strength site with tetrahedral symmetry.

Full Text

Duke Authors

Cited Authors

  • Benos, DJ; Mandel, LJ; Simon, SA

Published Date

  • August 1, 1980

Published In

Volume / Issue

  • 76 / 2

Start / End Page

  • 233 - 247

PubMed ID

  • 6251157

Pubmed Central ID

  • PMC2228591

International Standard Serial Number (ISSN)

  • 0022-1295

Digital Object Identifier (DOI)

  • 10.1085/jgp.76.2.233


  • eng

Conference Location

  • United States