Cadmium-induced decrease in the outer facing skin resistance of a bullfrog (Rana catesbeiana)

Effects of cadmium on the electrical properties of frog skin were investigated by using the microelectrode technique. The epidermal application of 2 mM Cd for 5 min increased both the short circuit current and the skin potential, and decreased the skin resistance (RM). Cadmium also decreased intracellular potential with reference to the epidermal solution (PDi) and the electrical resistance between the epidermal solution and the tip of a microelectrode (RM1) located in the stratum germinativum. deltaRM that is RM,Cd-RM, control seemed to approximately coincide with deltaRM1 which is RM1,Cd-RM1,control. Comparing with our previous results, i.e., Cd decreased RNa (the resistance to the active Na current) and increased Rsigma (the resistance to the passive ions) but did not altered ENa (the electromotive force of active Na current) in the later stage (15 min or later). Cd seemed to decrease the RNa component at the epidermal side of the skin in the early stage (less than 5 min).