Assay of melanotropic peptides in an in vitro mammalian system

A reproducible and sensitive assay for melanotropic agents is described employing mouse melanoma cells in culture and measuring tyrosinase activity in terms of production of tritiated water from L-(ring-3,5-3H)-tyrosine. Molar concentrations of peptides inducing one-half maximal stimulation of tyrosinase activity were: beta-MSH, 1 +/- 2 x 10(-9); alpha-MSH and Beta h-LPH, 1 +/- 2 x 10(-8); ACTHp, 1 +/- 2 x 10(-7). Beta p 9-18-MSH and melanotropin potentiating factor, beta s 88-91-LPH exhibited no activity at concentrations as high as 10(-5)M.