Existence of different forms of adrenocorticotropin in rat hypothalamus

Adrenocorticotropin (ACTH)-like immunoreactivity and bioactivity were extracted from rat hypothalamus and fractionated by high pressure liquid chromatography. Analysis of the fractions either by radioimmunoassay or bioassay (corticosteroid production from rat adrenal cells) revealed several peaks of immunoreactivity and bioactivity. Only 20-25% of total ACTH-like immunoreactivity and bioactivity eluted with the same retention time as authentic ACTH 1-39. The results suggest that different forms of ACTH exist in rat hypothalamus.