Adenylate Cyclase Induces Intracellular Ca2+ Increase in Single Human Epidermal Keratinocytes of the Epidermal Sheet As Measured by Digital Imaging Microscopy Using Fura 2-AM

Intracellular Ca2+ ([Ca2+]i) is thought to act as a second messenger of transmembrane signalling systems. However, no measurement of [Ca2+]i has been made in intact epidermal keratinocytes. We have developed a method for measuring [Ca2+]i in human keratinocytes from pure epidermal sheet by the application of digital imaging fluorescence microscopy with the use of Fura 2-AM. Normal human pure epidermal sheets were obtained by dispase treatment. Epinephrine and salbutamol induced transient [Ca2+]i increases. Propranolol, a beta-antagonist, inhibited this response, while prazosin and yohimbine (alpha 1- and alpha 2-antagonists, respectively) did not affect the response. Histamine and adenosine, also receptor agonists of the epidermal adenylate cyclase system, induced a similar [Ca2+]i increase, as did forskolin, a direct activator of adenylate cyclase. These data coincide with those previously presented for cultured human epidermal keratinocytes, and reveal that adenylate cyclase activation induces an increase of [Ca2+]i in intact epidermal cells. This technique enables the kinetics of [Ca2+]i in various skin disorders to be investigated.