Abstract
1. The instantaneous impedance method has been used to study the effects of antidiuretic hormone (ADH) on frog skin.2. The resting skin may be represented by a parallel RC network with a single time constant.3. Antidiuretic hormone causes an increase in conductance and capacitance and in some cases the appearance of a polarization angle.4. The structures in the skin responsible for the transients are located in the outermost membranes.5. The effects of ADH have been interpreted in terms of the formation of water-filled sodium-permselective pores in the outer facing membranes which occupy, at most, 0.3% of the skin surface. These pores constitute a parallel, and hence additive, capacitance with that of the normally ion impermeable parts of the cell surface, and in addition are responsible for the increase in conductance. The polarization angle is due to the polydisperse nature of the skin after hormone treatment.