A new method of the measurement of the electrically neutral fluxes of cations through lipid bilayer membranes induced by Men+/nH+-exchangers

Electrically neutral ionophores (nigericin, monencin) incorporated into a planar bilayer lipid membrane (BLM) bring about hydrogen ion gradient formation in the unstirred layers of BLM if a metal ion gradient on the membrane is prepared. Under these conditions a diffusion potential of a hydrogen ion is generated after addition of a protonophore. Cation selectivity of nigericin, monencin and A23187 has been studied by means of electrical potential measurements in the presence of a protonophore and Men+/nH+-exchangers mentioned above. The data on cation selectivity are in a good agreement with the well known results of the direct measurements of metal ion fluxes. This shows that the effect of generation of the potential on BLM in the presence of a protonophore and a Men+/nH+-exchanger can be used for the estimation of electrically neutral ion fluxes through BLM.