RESUMO
The purpose of this study was to determine the effect of melanin on skin response to single 3.8-microm, 8-micros laser pulses and the difference in lesion formation thresholds. Our hypothesis was that pigmentation would play a significant role in skin energy absorption at 3.8 microm. Previous studies comparing pigmented and lightly pigmented porcine skin with human skin found that compared with Yorkshire pigs, Yucatan minipigs were a superior model for laser skin exposure because of their higher pigmentation levels. In the current study, 10 pigs under general anesthesia were exposed to 3.8-microm laser pulses ranging from 0.01 J/cm2 to 93 J/cm2. Gross examinations and skin biopsies were done 24 h after laser exposure, and histologic examinations were conducted on these tissue samples. The 24-h effective dose (ED50) was determined to be 4.5 J/cm2 for Yucatan mini-pigs and 2.6 J/cm2 for Yorkshire pigs. As deposited energy was increased, the lesion presentation progressed from desiccation of the superficial layer of epidermis (4 J/cm2) to desiccation with inflammatory centers (14 J/cm2), and finally to replacement of inflammatory areas with an epidermal ulcerated central area (=21 J/cm2). Therefore we found no statistical difference between the 24-h ED50 of the 2 breeds of pigs, nor was there any difference in histologic presentation at 24 h postexposure.