Amiloride stimulation of sodium transport in the presence of calcium and a divalent cation chelator

Thurman, C.L.; Higgins, J.T.

Biochimica et Biophysica Acta 689(3): 561-566


ISSN/ISBN: 0006-3002
PMID: 6812629
DOI: 10.1016/0005-2736(82)90314-5
Accession: 004708512

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Amiloride in nanomolar to micromolar concentrations stimulates the short circuit current (Isc) of the toad urinary bladder by as much as 120% when applied in conjunction with apical Ca2+ and a divalent cation chelator. A significant decrease in transepithelial resistance (Rt) is observed simultaneously. This response is spontaneously reversible and its amplitude is dependent upon apical Na+ concentrations. The stimulated Isc persisted when acetazolamide (1 mM) was introduced, HPO42- substituted for HCO3- or SO42- replaced Cl-. The increase in Isc is not due to the change of Cl-, H+ or HCO3- flux. This behavior in a tight epithelium may be related to the mechanism controlling apical Na+ permeability.