Comparative effects of ionophores grisorixin, alborixin and two derivatives on K+ glutamate efflux in rat liver mitochondria.

The alkali cations discrimination on a liquid membrane electrodes system, was determined for the carboxylic ionophores grisorixin, alborixin and two derivatives, dihydrogrisorixin and hexahydroalborixin. The two antibiotics exhibited a great perference for K+. Dihydrogrisorixin again showed the selectivity curve of a carboxylic ionophore, but with a discrimination power lowered compared with grisorixin. Hexahydroalborixin had lost all the complexing properties of the natural molecule. The selectivity scales measured for cations, were directly correlated with the K+ and glutamate effluxes measured in rat liver mitochondria. The chemical modifications of the natural structures of grisorixin and alborixin resulted in a drastic reduction of their ionophoric properties. The loss of K+-glutamate might occur in two steps, the efflux of K+ catalysed by the ionophores then causing a loss of negative charges in the form of glutamate.