Gniadecka M, Wulf H C, Mortensen N N, Poulsen T
Department of Dermatology, National University Hospital Copenhagen, Denmark.
Acta Derm Venereol. 1996 Nov;76(6):429-32. doi: 10.2340/0001555576429432.
Pigmentation, stratum corneum and viable epidermis are considered to be the main factors protecting against ultraviolet radiation. We quantitatively investigated the degree of photoprotection provided by these structures in vitiligo and adjacent normally pigmented skin. In 14 patients 61 MED tests were performed in vitiligo and adjacent normally pigmented skin using a solar simulator. The thickness of stratum corneum and viable epidermis was determined from frozen skin sections, and pigmentation was calculated by measuring skin reflectance at 555 nm and 660 nm. To analyse photoprotection, the UV dose necessary to evoke erythema was regressed against the thickness of stratum corneum and viable epidermis, pigmentation and the erythema grade in the MED test. By analysing regression coefficients we found that stratum corneum was the main photoprotective factor not only in vitiligo but also in normally pigmented skin. The effect of pigmentation in normal skin was slightly less prominent. Stratum corneum was thicker in vitiligo than in normally pigmented skin. However, the photoprotection due to stratum corneum was similar in both groups because significantly less photoprotection was achieved per thickness unit of stratum corneum in vitiligo than in normal skin. Neither in vitiligo nor in normally pigmented skin did the photoprotection depend on viable epidermis. Our data quantitatively document the importance of stratum corneum and pigmentation. Hyperkeratosis in vitiligo offers just as efficient photoprotection as does the normal stratum corneum in pigmented skin.
色素沉着、角质层和有活力的表皮被认为是抵御紫外线辐射的主要因素。我们定量研究了这些结构在白癜风及相邻正常色素沉着皮肤中提供的光保护程度。对14例患者使用太阳模拟器在白癜风及相邻正常色素沉着皮肤中进行了61次最小红斑量（MED）测试。从冷冻皮肤切片中测定角质层和有活力表皮的厚度，并通过测量555nm和660nm处的皮肤反射率来计算色素沉着。为了分析光保护作用，将诱发红斑所需的紫外线剂量与角质层和有活力表皮的厚度、色素沉着以及MED测试中的红斑等级进行回归分析。通过分析回归系数，我们发现角质层不仅是白癜风皮肤也是正常色素沉着皮肤的主要光保护因素。正常皮肤中色素沉着的作用稍不明显。白癜风皮肤的角质层比正常色素沉着皮肤的厚。然而，两组中角质层提供的光保护作用相似，因为白癜风皮肤中每单位厚度角质层所实现的光保护作用明显低于正常皮肤。在白癜风皮肤和正常色素沉着皮肤中，光保护作用均不依赖于有活力的表皮。我们的数据定量证明了角质层和色素沉着的重要性。白癜风中的角化过度提供的光保护作用与色素沉着皮肤中的正常角质层一样有效。
