Ultraviolet Action Spectrum for Intracellular Free Ca²⁺ Increase in Human Epidermal Keratinocytes

Abstract

Effects of UV on normal human epidermal keratinocytes were studied by measuring the intracellular free Ca²⁺ concentration ([Ca2⁺]i) using fluorescence ratio imaging (fura-2-AM). Upon UV irradiation the [Ca²⁺]i increased sharply after a certain lag time, and the UV sensitivity was higher at lower temperatures. Statistically the distribution of [Ca²⁺]i became broader as the mean values became larger, and the number of affected cells increased sharply above a certain fluenee (light intensity x time [photons/cm²]) at all wavelengths studied (200-400 nm). The action spectrum showed a single peak at about 230 nm and decreased gradually toward longer-wavelength UVregions.