Increased melanin pigmentation following ultraviolet irradiation is due to increasing tyrosinase activity and multiplication of functioning melanocytes. After UV-irradiation, the size of melanocytes increases, and melanocyte dendrites elongate
and
branch.
In this experiment, we induced the activation of melanocytes in the epidermis of C57BL black mice by ultraviolet-B (UVB) irradiation and observed the effect of azelaic acid and retinoic acid on the UVB activated epidermal melanocytes.
Sixty C57BL black mice were irradiated by UVB 100mJ/㎠ daily for 10 days, and then azelaic acid and retinoic acid wre topically applied daily for 7 weeks.
For the estimation of morphologic change of epidermal melanocytes, light microscopic observation with split DOPA stain was performed at the end of the 1st, 3rd, 5th and 7th week of topical application.
@ES The results are summerized as follows :
@EN 1. The number, size and circumference of DOPA-positive epidermal mealanocytes were significantly decreased in 20% azelaic acid applied group and 20% azelaic acid and 0.05% retinoic acid applied group.
2. In 20% azelaic acid and 0.05% retinoic acid applied group, the number, size and circumference of DOPA-positive epidermal melanocytes were more significantly decreased than in 20% azelaic acid applied group.
In summary, the present study suggets that azelaic acid acts as a depigmenting agent on epidermal melanocytes and such depigmenting effect of azelaic acid was increased by addition of retinoic acid. (Kor J Dermatol 1992 ; 30 (4) : 492-498)
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