Intracellular calcium response to high temperature is similar in undifferentiated and differentiated cultured human keratinocytes.

A series of thermo-sensitive proteins is expressed in epidermal keratinocytes, where they function as cation channels that are activated at temperatures in the range of 28-42°C. Here, we examined the influence of high temperature on intracellular calcium level in undifferentiated and differentiated cultured human keratinocytes, which are considered to be representative of deeper and upper epidermal layers, respectively. We found that the percentages of responsive keratinocytes among undifferentiated and differentiated cells exposed to temperatures in the warm-hot range (30-50°C) were essentially the same. In contrast, we previously demonstrated that undifferentiated keratinocytes were more sensitive than differentiated cells to low temperature (<22°C). Thus, the deeper layer of the epidermis is more sensitive to cold than the upper layer, but the response to warm-hot temperatures appears to be homogeneous throughout the epidermis.