No abstract

Melanocytes were successfully established from involved and uninvolved skin of a patient with acute acrofacial vitiligo. Cells from involved epidermis showed a fivefold decrease in the rate of radiolabelled 45Ca uptake compared with uninvolved and control cells. These results are similar to previous findings in keratinocytes from involved skin in patients with vitiligo. Since 6-biopterin is cytotoxic to melanocytes and calcium controls the redox status of the 6-biopterin/(6R)5, 6, 7, 8-tetrahydrobiopterin equilibrium via the thioredoxin reductase/thioredoxin system, these results underline the importance of this electron transfer system for both melanocyte function and survival.

Melanocytes were successfully established from involved and uninvolved skin of a patient with acute acrofacial vitiligo. Cells from involved epidermis showed a fivefold decrease in the rate of radiolabelled 45Ca uptake compared with uninvolved and control cells. These results are similar to previous findings in keratinocytes from involved skin in patients with vitiligo. Since 6-biopterin is cytotoxic to melanocytes and calcium controls the redox status of the 6-biopterin/(6R)5, 6, 7, 8-tetrahydrobiopterin equilibrium via the thioredoxin reductase/thioredoxin system, these results underline the importance of this electron transfer system for both melanocyte function and survival.

SummaryActivity of tyrosinase directly controls melanogenesis in the human epidermis. Recently, it has been shown that the biosynthesis and recycling of (6R)L-erythro 5,6,7,8 tetrahydrobiopterin (6-BH4) plays a central role in regulating the supply of L-tyrosine, the substrate for tyrosinase. In this report, we present ~\·idence that 6-BH. and other tetrahydropterins, have the capacity to regulate tyrosinase activity directly :--y a specific uncompetitive mechanism. This fine control of tyrosinase activity/melanogenesis in the human ~;-,idermis depends on the redox equilibrium 6-BH. ~ dihydropterin ~ 6-biopterin. The accumulation of t>-biopterin is cytotoxic to normal human melanocytes.