MEMBRANE POTENTIALS, RESISTANCE, AND ION PERMEABILITY IN SQUID GIANT AXONS INJECTED OR PERFUSED WITH PROTEASES

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Abstract
Since external application of proteases seems not to interfere with electrical function of squid, lobster, or frog axons, participation of protein in membrane physiology has been thought by some to be doubtful. The following findings indicate that the protein in the inner surface of the excitable membrane of an axon is available to proteolytic action in contrast to the protein of the outer surface: Intracellular microinjection of protease affects both resting potential and action potential. The temporal sequence of protease-in-duced changes suggests that protein is somehow involved in impulse generation. Intracellular microinjection of protease affects membrane resistance. There is a considerable decrease in resistance to hyper-polarizing currents. Intracellular microinjection of protease increases both sodium and potassium effluxes. There is an excellent agreement and consistency between the temporal sequences of protease-induced changes determined by measuring membrane potentials, membrane resistance, and membrane permeability. The present communication, therefore, demonstrates that cell surface protein integrity is essential for maintenance of cell membrane properties and physiology.