Gonadotropin-releasing hormone-associated peptide immunoreactivity in bovine colostrum

Gonadotropin-releasing hormone(GnRH)-associated peptide (GAP) is a 56-amino acid peptide found on the C-terminal of the GnRH (also called luteinizing hormone-releasing hormone) precursor and is assumed to be co-produced with GnRH. The purpose of this report is to demonstrate the presence of GAP immunoreactivity in bovine colostrum. Radioimmunoassay of acidified methanolic extracts demonstrated a concentration of GAP immunoreactivity of approximately 1.5 +/- 0.1 pmol/g dry skim bovine colostrum. Gel filtration (Sephadex G-10) and high-performance liquid chromatography of extracts containing GAP immunoreactivity showed it to be of low molecular weight and a high hydrophobic character. The presence of GAP immunoreactivity in bovine colostrum suggests that the GnRH precursor is synthesized and processed in mammary tissue itself.