R. Bhardwaj et al., Pharmacologic response of a controlled-release PLGA formulation for the alpha-melanocyte stimulating hormone analog, melanotan-I, PHARM RES, 17(5), 2000, pp. 593-599
Purpose. The objective of this study was to evaluate in vitro and in vivo t
he melanogenic activity of one-month duration Melanotan-I (MTI) implants pr
epared using poly (D,L lactide-co-glycolide) polymer.
Methods, The biological activity of the samples of MT-I released in vitro f
rom the non-irradiated or gamma irradiated implants was measured using a fr
og skin bioassay. The effect of MT-I on skin pigmentation was measured usin
g a Chroma meter (reflectometer) after subcutaneous administration of impla
nts 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 concentra
tion of a freshly prepared MT-1 standard. The reflectance readings demonstr
ated 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 eu
melanin 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.