Some Effects of Chemical Irritants on the Membrane of the Giant Amoeba

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.