PURPOSE: The objective of this study was to evaluate in vitro and in vivo the melanogenic activity of one-month duration Melanotan-I (MT-I) implants prepared using poly (D,L lactide-co-glycolide) polymer. METHODS: The biological activity of the samples of MT-I released in vitro from the non-irradiated or gamma irradiated implants was measured using a frog skin bioassay. The effect of MT-I on skin pigmentation was measured using a Chroma meter (reflectometer) after subcutaneous administration of implants containing 4 mg MT-I to guinea pigs. Eumelanin, the black/brown melanin pigment, was quantified in skin biopsies as pyrrole-2, 3, 5-tricarboxylic acid using HPLC. RESULTS: The MT-I released in vitro from implants after 24 hours exhibited 100% melanotropic activity in frog skins compared to an identical concentration of a freshly prepared MT-I standard. The reflectance readings demonstrated a prolonged skin darkening for up to three months as evidenced by the decrease in the luminance values from 0 to -4.82. A 2.5-fold increase in eumelanin levels was observed after one month and the increased pigmentation lasted for 3 months. CONCLUSIONS: The melanogenic response to MT-I implants persisted for three months and the increase in pigmentation, especially the increased eumelanin levels, could provide protection from ultraviolet radiation.
PURPOSE: The objective of this study was to evaluate in vitro and in vivo the melanogenic activity of one-month duration Melanotan-I (MT-I) implants prepared using poly (D,L lactide-co-glycolide) polymer. METHODS: The biological activity of the samples of MT-I released in vitro from the non-irradiated or gamma irradiated implants was measured using a frog skin bioassay. The effect of MT-I on skin pigmentation was measured using a Chroma meter (reflectometer) after subcutaneous administration of implants containing 4 mg MT-I to guinea pigs. Eumelanin, the black/brown melanin pigment, was quantified in skin biopsies as pyrrole-2, 3, 5-tricarboxylic acid using HPLC. RESULTS: The MT-I released in vitro from implants after 24 hours exhibited 100% melanotropic activity in frog skins compared to an identical concentration of a freshly prepared MT-I standard. The reflectance readings demonstrated a prolonged skin darkening for up to three months as evidenced by the decrease in the luminance values from 0 to -4.82. A 2.5-fold increase in eumelanin levels was observed after one month and the increased pigmentation lasted for 3 months. CONCLUSIONS: The melanogenic response to MT-I implants persisted for three months and the increase in pigmentation, especially the increased eumelanin levels, could provide protection from ultraviolet radiation.
Authors: S O Ugwu; J Blanchard; R T Dorr; N Levine; C Brooks; M E Hadley; M Aickin; V J Hruby Journal: Biopharm Drug Dispos Date: 1997-04 Impact factor: 1.627
Authors: M E Hadley; J H Mieyr; B E Martin; A M Castrucci; V J Hruby; T K Sawyer; E A Powers; K R Rao Journal: Comp Biochem Physiol A Comp Physiol Date: 1985
Authors: T K Sawyer; P J Sanfilippo; V J Hruby; M H Engel; C B Heward; J B Burnett; M E Hadley Journal: Proc Natl Acad Sci U S A Date: 1980-10 Impact factor: 11.205