| Autor: |
Hearing, V. J., Yamaguchi, Y., Tadokoro, T., Zmudzka, B. Z., Miller, S. A., Beer, J. Z. |
| Předmět: |
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| Zdroj: |
Pigment Cell Research; Aug2004, Vol. 17 Issue 4, p440-441, 2p |
| Abstrakt: |
Melanin affords some protection against UV-induced DNA damage, and people with darker skins have significantly lower skin cancer incidence. The exact role(s) of melanin in photoprotection and melanocyte responses to UV in human skin of different colors have not been detailed. In this study, the skin of subjects from several racial/ethnic groups was exposed to 1 MED of UVA/UVB radiation. Biopsies were taken before, and 7 min, 1 d, and 1 week after UV exposure and examined using melanocyte-specific antibodies (to MITF, TYR, GP100, etc.). The density of functional melanocytes in unexposed skin was remarkably similar in ‘White’, ‘Asian’ and ‘Black or African-American’ skin although basal melanin contents differed dramatically. UV did not markedly increase the density of melanocytes in any type of skin within a week. Importantly, darker skin was generally more responsive to UV, and melanocytes in such skin slightly increased their production of melanogenic enzymes and of melanin after 1 week, whereas lighter skin showed no or very small increases. Darkening of skin (development of a tan assessed visually and by reflectance measurements) strongly depended on constitutive color: >1 MED was needed for tanning of light skin, while a deep tan was produced by 1 MED in dark skin. Thus, the appearance of the skin depended on redistribution of existing pigment in the epidermis. It is clear from these results that early changes associated with tanning result from increased interactions of melanocytes and keratinocytes to transfer and distribute existing melanin. Increases in melanocyte density and production of melanin only occur at later time points. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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