[In vitro study of various ionophore antibiotics and some of their derivatives. II. Characterization of the ionophore properties of the compounds in a model system for Na+ and K+ ions].

Transport of Na+ and K+ by different carboxylic polyether antibiotics and some of their derivatives was measured in a triphasic water/chloroform/water model system. Monensin, nigericin, narasin and lasalocid proved to be efficient K+ carriers, while grisorixin, alborixin and X 14547A gave lower ionic fluxes. Furthermore, the structural modifications of nigericin, grisorixin and lasalocid reduced the ionophore properties of the corresponding natural metabolite. Monensin was also characterized as a good Na+ carrier. Cation transport results were in keeping with those of a previous study on the end-products of rumen fermentation. In both cases monensin, nigericin, narasin and lasalocid were the most efficient compounds.