SOME EFFECTS OF CHEMICAL IRRITANTS ON THE MEMBRANE OF THE GIANT AMOEBA

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Abstract
The effects of chemical irritants on the membrane potential and input resistance of the giant amoeba, Chaos carolinense, have been investigated. The membrane potential and input resistance were −111.5 mV and 8.6 MΩ respectively In the resting state the cell membrane of Chaos carolinense was found to be impermeable to Na+ but permeable to K+. The distribution of K+ across the cell membrane conformed to a Donnan equilibrium with the resting membrane potential being the K+ equilibrium potential The chemical irritants dibenzoxazepine and its 2‐chloro‐ and 3‐chloro‐analogues and o‐chlorobenzylidene malononitrile produced a fall in input resistance but no change in membrane potential. It is suggested that these effects are caused by an increase in K+ permeability The potencies of a series of chemical irritants with respect to dibenzoxazepine were measured on the giant amoeba. These potencies did not reflect those found in mammalian preparations.