COMPARATIVE POTENCY OF BROAD-BAND AND NARROW-BAND PHOTOTHERAPY SOURCES TO INDUCE EDEMA, SUNBURN CELLS AND UROCANIC ACID PHOTOISOMERIZATION IN HAIRLESS MOUSE SKIN

The Philips TL01 narrow-band (311-313 nm) fluorescent lamp provides ef fective phototherapy for psoriasis and atopic eczema while emitting le ss erythemogenic radiation than conventional broad-band (e.g. Philips TL12; 270-350 nm) sources. We studied the potency of TL01 and TL12 rad iation to induce edema and sunburn cells (SBC) and to photoisomerize n aturally occurring trans-urocanic acid (UCA) to cis-UCA in hairless mo use skin. Cis-UCA has immunosuppressive properties and is a putative m ediator of UV-induced suppression of immune responses. For each source , there was UV dose dependence for all three responses. Within the dos e ranges used, the potency ratio of TL12:TL01 radiation to induce equi valent edema and SBC was about 6:1. However, the potency ratio to indu ce cis-UCA was less than 2.3:1. Therefore, at a given level of edema o r SBC induction, TL01 was more efficient than TL12 at UCA photoisomeri zation. The TL01 induction of immunomodulating cis-UCA, while causing minimal skin injury, may relate to the therapeutic efficacy of this so urce in skin conditions with an immunological component.