MAMMALIAN PIGMENTATION .1. INHIBITORS OF DOPA AUTOXIDATION IN EXTRACTS OF HUMAN AND MOUSE SKIN

[摘要] Aqueous extracts of human and mouse skin were tested for inhibitory action on autoxidation of L-DOPA to melanin in vitro. Regardless of status of hair growth all extracts of skin from albino (Strong A) mice inhibited dopa oxidation. Skin extracts from pigmented (PBR) mice were inhibitory when hair was resting and when hair bulbs were excluded from skin samples with growing hair follicles and enhanced melanin formation, presumably owing to release of tyrosinase from hair bulbs. Following heat in-activation of tyrosinase, enhancing extracts inhibited melanin synthesis. Extracts of scalp and abdominal skin from human cadavers were inhibitory. With the exception of human abdominal corium, values obtained for melanogenic inhibition of human and mouse skin were similar when expressed as a function of dry weight of tissue extract. The inhibitory factor in both human and mouse skin is at least in part nondialyzable and consists of no less than 2 fractions; one apparently sulfhydryl in nature and heat-labile, and another non-sulfhydryl and heat stable. Such inhibitors would appear to be important in regulating rates of melanin formation in vivo and also as part of a general system of biological antioxidants.