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, proliferate 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 extracellular 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.