Potassium Conductance of Skeletal Muscle treated with Formaldehyde

Abstract

HISTOLOGICAL fixatives act by combining with and forming links between reactive groups of biological molecules, but even in the usual strong concentrations they do not destroy all chemical and physical properties of the original living material. The activity of some enzymes, for example, remains after fixation¹. Recently the effect on excitable membranes of weak solutions of fixatives has been examined with electrophysiological techniques which allow the results of physico-chemical changes to be followed as they develop. In cardiac Purkinje fibres the plateau phase of the action potential is prolonged by formaldehyde². In skeletal muscle the usually brief action potential acquires a long-lasting plateau during exposure to formaldehyde³. Because the conductance of the skeletal muscle membrane is high during the induced plateau, formaldehyde can be supposed to act either by slowing the inactivation of the sodium conductance or by causing a loss of specificity of the more slowly operating potassium conductance system in favour of sodium³. A prolongation of the action potential of probably similar nature has also been reported in crayfish nerve fibres exposed to various aldehydes⁴.