Characterization of corticotropin-like immunoreactive peptides in rat brain using high performance liquid chromatography.

The molecular nature of corticotropin (ACTH)-related peptides in rat brain has been studied using high performance liquid chromatography (HPLC) and radioimmunoassay. The major ACTH-immunoreactive species in rat hypothalamic extracts coelutes with corticotropin-like intermediate lobe peptide (CLIP); ACTH18-39) on two HPLC solvent gradients, and has 3-4 times more C-terminal than N-terminal immunoreactivity. N-terminal ACTH-immunoreactivity is composed of a number of peaks on HPLC with less than 10% eluting at the position of ACTH. Hypothalamic C-terminal ACTH immunoreactivity is also heterogeneous and resembles in some respect that seen in the rat neuro-intermediate lobe. Around 90% of the alpha-MSH immunoreactivity in the hypothalamus elutes as a single peak in the position of des[N-acetyl] alpha -MSH (ACTH1-13-NH2).