EFFECTS OF ACTIVE TRANSPORT INHIBITORS ON K MOVEMENTS IN ACANTHAMOEBA SP.

Abstract

The effects of known inhibitors of active cation transport were investigated on K permeability and content of Acanthamoeba sp. The inhibitors could be divided into three types: ( a ) hypothermia (5°C) caused a shift in the equilibrium of cell K from the exchangeable to the nonexchangeable fraction, with little or no net loss of cell K; ( b ) hypertonicity and CO 2 caused a net loss of cell K from the exchangeable fraction to the environment; and ( c ) He and 2,4-DNP caused a combination of these two effects. All of the inhibitors caused a specific reduction of the transfer coefficient for K entry relative to that for K efflux. It was concluded that this amoeba possessed an active transport mechanism to maintain cell K against a concentration gradient, but not to extrude cell Na under the conditions tested. Ouabain, the classical active cation transport inhibitor, had no effect on this type of K transport. It was suggested that Ouabain is a specific inhibitor of active Na transport and active K transport when it is coupled to Na transport, but does not inhibit active K transport when it is independent of Na.