The use of 60Co-EDTA as an extracellular marker in frog skin

60Co-EDTA was tested as an extracellular marker in isolated epithelia of frog skin. It was found to be non-toxic for frog skin and 0.1 mM EDTA proved to be enough to saturate any adsorption sites. Comparing with [14C]inulin, 60Co-EDTA marks a slightly greater extracellular space and this volume is constant between 15 min and 2 h. Furthermore it is reproducible and its use simplifies the methodology of the determination of water and electrolyte contents in the cells.