Dose dependence of glutaraldehyde-induced changes in the electrical properties of the amphibian skin

Abstract

The effects of the protein cross-linker glutaraldehyde (GA) on the transepithelial short-circuit current (I_sc), conductance (G_t) and impedance of the isolated frog skin were investigated at GA concentrations between 0.1 and 10 mm, i.e. up to three orders of magnitude less than used in fixative procedures. Below 0.5 mm GA increases I_sc, with large variations among preparata. Millimolar GA concentrations induce fairly reproducible irreversible inhibitions of I_sc, which proceed for about 3 h. The rate of I_sc decrease and the amplitudes of the initial drop and subsequent recovery depend on GA concentration in a sigmoidal dose-effect way, reaching saturation at 10 mM. At this GA concentration, G_t is increased up to 5 times the control value. Transepithelial impedance measurements confirm the decreases in epithelial resistance (R_m) and show significant increases in epithelial capacitance (C_m). R_m is diminished by 20% at 0.5 mm GA and by 75% at 10 mm GA, while C_m is maximally augmented by 55% at 2.5 mm GA. It is concluded that protein cross-linking by mild GA treatment is a convenient procedure for changing the electrical characteristics of epithelia.