Effect of current, ionic strength and temperature on the electrical properties of skin

Abstract

The complex electrical impedance of hairless mouse skin was measured as a function of frequency, and resistance and capacitance were determined. Increasing the ionic strength of the bathing medium, and increasing the magnitude of current, decreased resistance, whereas capacitance was, in general, unchanged. These changes occurred rapidly. The decrease in resistance with increasing the ionic strength of the bathing medium was consistent with elevated ion levels within the ion-conducting pathways of the membrane. The decrease in resistance by increasing the magnitude of current seems to be related to alteration of the current-conducting pathway. With increasing temperature, resistance also decreased while capacitance increased. The activation energy for ion conduction through the skin was estimated to be 3.4 kcal/mol at physiologically relevant temperatures. The most marked changes occurred at the phase transition temperature (60°C) of the stratum corneum (SC) lipids; resistance fell dramatically and capacitance steadily increased — ultimately, the impedance became independent of frequency, suggesting that the capacitive properties of the barrier had been lost. Overall, the results provide mechanistic insight into ion conduction through the skin and into the role of SC lipids in skin capacitance.