Extracellular calcium affects the membrane currents of cultured human keratinocytes

Electrophysiologic properties of cultured human keratinocytes were studied using the patch voltage‐clamp technique. Undifferentiated, proliferative keratinocytes grown in low Ca2+ medium had an average resting membrane potential of −24 mV. Voltage‐clamp experiments showed that these cells had two membrane ionic currents: a large voltage‐independent leak conductance, and a smaller voltage‐dependent Cl− current that activated with depolarization. Increasing the extra‐cellular Ca2+ concentration from 0.15 to 2 mM resulted in a doubling of the magnitude of the voltage‐gated current and a shift in current activation to more negative potentials. Since levels of extracellular Ca2+ can alter the morphology and differentiation state of keratinocytes, the finding of a Ca2+ ‐activated Cl− current in these cells suggests a role for this conductance in the initiation of differentiation.