Quantitative Assay of Melanophore-Expanding Property of Preparations of ACTH and Corticotropin B

Summary Skin melanophores of freshly amputated tadpole tails expand when placed in solutions of ACTH. An assay for rapid estimation of this melanophore-expanding activity of ACTH preparations has been developed, using USP corticotropin as the Reference Standard. All ACTH preparations tested showed this activity. Corticotropin B; the most highly purified preparation available, showed the highest degree of melanophore-expanding activity and was also the most potent in causing adrenal ascorbic acid depletion.