Characterization of the alpha-MSH-like immunoreactivity in blood and cerebrospinal fluid of the rat

We have investigated the nature of the alpha-melanocyte stimulating hormone-like immunoreactivity (alpha-MSH-LI) in blood and cerebrospinal fluid (CSF) of the rat. Blood and CSF from intact animals were subjected to high pressure liquid chromatography (HPLC) followed by a radioimmunoassay (RIA) specific for the C-terminal part of the alpha-MSH molecule. It appeared that in both body fluids the predominant alpha-MSH-LI co-migrated with synthetic alpha-MSH and not with its des-acetyl or di-acetyl analogues. We conclude that alpha-MSH is the predominant form of alpha-MSH-LI circulating in plasma and CSF of rats from our Wistar strain.