POSSIBLE MECHANISMS OF VASCULAR RELAXATION INDUCED BY PULSED-UV LASER

This study was designed to examine the mechanism of vasorelaxation ind uced by pulsed-UV laser. Luminal diameters of rat femoral arteries wer e measured prior to and following krypton-fluoride excimer laser irrad iation of 248 mn in wavelength. The diameter was enlarged to 1.3 times the preirradiated size at 1 or 10 Hz irradiation when the fluence was over 2.0 mJ/pulse/mm(2), while the diameter reached 1.8 times at 100 Hz with a fluence of 0.8 mJ/pulse/mm(2). Vasorelaxation by the 100 Hz irradiation was inhibited when the artery was pretreated with methylen e blue but was enhanced with superoxide dismutase, Pathological analys is revealed an ablation crater and vacuole formation in the vessel at 1 or 10 Hz irradiation, but these changes were not remarkable in the 1 00 Hz-exposed sample. These findings suggest that vasorelaxation induc ed by the pulsed UV irradiation at 1 or 10 Hz results from structural alteration of vascular smooth muscle by the ablation crater or vacuoli zation, On the other hand, a possible mechanism of vasorelaxation at t he 100 Hz irradiation is partially related to nitric oxide.