Phloretin-induced changes in ion transport across lipid bilayer membranes.

Abstract

Phloretin, the aglucone derivative of phlorizin, increases cation conductance and decreases anion conductance in lipid bilayer membranes. Evidence showing that phloretin acts almost exclusively by altering the permeability of the membrane interior and not by modifying the partition of the permeant species between the membrane and the bulk aqueous phases was based on an alysis of the current responses to a square boltage pulse obtained for the lipophilic anion, tetraphenylborate and the cation complex, peptide PV-K+. These results are consistent with the hypothesis that phloretin decreases the intrinsic positive internal membrane potential but does not modify to a great extent the potential energy minima at the membrane interfaces. Phloretin increases the conductance for the nonactin-K+ complex, but above 10-5 M the steady-state nonactin-K+ voltage-current curve changes from superlinear to sublinear. Above 10-5 M phloretin, the nonactin-K+ transport across the membrane becomes interfacially limited.