Immunohistochemical Localization of Drugbinding Protein in Tissues of the Electric Eel

Abstract

A PROTEIN having a high affinity for d-tubocurarine has been isolated from ammonium sulphate fractions of extracts of electric organ of electric eel^1,2. Although d-tubocurarine combines with a variety of macromolecules^3–5, the reaction with the electric organ protein appeared to be somewhat unique, especially since the resulting complex is very stable to high ionic strength¹. The protein also combines in a more or less specific way with a large number of neurotropic compounds, the relative affinities in general paralleling the effectiveness of these compounds in their pharmacological action upon the single isolated electroplax^1,2,5,6 and squid giant axon^7,8. Although it was proposed^1,2 that the protein might function in vivo as a ‘receptor’ for acetylcholine and other neurotropic compounds, more recent evidence has led to a suggestion of an entirely different role^9,10, namely, that the protein might be the drug-binding component of conducting membranes only and thus is not involved in the physiological effects of acetylcholine and other depolarizing agents. The distribution of this material in the electroplax is thus of primary importance in determining whether or not the conclusions regarding its proposed biological significance are justified.