Air-exposed keratinocytes exhibited intracellular calcium oscillation.

We previously demonstrated that calcium propagation plays a crucial role in epidermal homeostasis when the epidermis was exposed to a dry environment. In the present study, we first demonstrated the intracellular calcium oscillation in cultured human skin keratinocytes. On partial exposure of cultured human keratinocytes to air, a transient increase of intracellular calcium concentration appeared, followed by a wave-like increase in the unexposed keratinocytes, showing oscillations with a frequency that varied from cell to cell. There appeared to be no correlation between the oscillation frequencies in adjacent cells. The increase of calcium concentration did not appear when calcium was removed from the medium or when suramin, a purinergic receptor antagonist, was added. The ATP concentration also increased immediately after keratinocytes were exposed to air. We hypothesize that ATP is secreted from keratinocytes on exposure to air, and induces an increase of intracellular calcium concentration.