The use of phospholipid-impregnated millipore filters for recording nonelectrogenic cation flows in the presence of Me/nH exchangers

It has been shown that with a cation (K⁺, Na⁺, Ca²⁺) concentration gradient on a Millipore filter impregnated with a decane solution of phospholipid, in the presence of a Meⁿ⁺/nH⁺ exchanger (nigericin, monensin, A23187), addition of a protonophore induces the formation of an electric potential positively charged on the side where the concentration of the cation is lower. The formation of the potential is induced by the hydrogen ion concentration gradient in the filter and in the unstirred layers as a result of the Meⁿ⁺/nH⁺ exchange. In such a system, with a pH gradient on the filter in the presence of monensin and valinomycin, a potential is generated with the plus on the side of the lower concentration of hydrogen. The effect is the result of the formation of a potassium ion concentration gradient in the unstirred layers in the course of the K⁺/H⁺ exchange. It is concluded that phospholipid-impregnated filters can be used for search and identification of electroneutral membrane ionophores of the Meⁿ⁺/nH⁺ exchanger type.