QUANTITATION AND IDENTIFICATION OF 2 CHOLECYSTOKININ PEPTIDES, CCK-4 AND CCK-8S, IN RAT-BRAIN BY HPLC AND FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY

A sensitive HPLC method has been described for quantitation of two cho lecystokinin (CCK) peptides in discrete rat brain regions. Separation and quantitation was performed by the reversed-phase HPLC combined wit h electrochemical detection. Analytical recoveries of the tetrapeptide (CCK-4) and octapeptide-sulphate (CCK-8s) were 96% and 94%, respectiv ely. The between assay coefficient of variation (CV) was less than 3% for both peptides. The within-assay CV was 4% and 6% for CCK-4 and CCK -8s and the detection limit was 2 and 10 pmol/mL, respectively. For id entification of structures, the peptides were fractionated by semi-pre parative HPLC using a novel SMART system for micropurification. The fr actions were analysed by fast atom bombardment mass spectrometry ( FAB MS) which confirmed the presence of both CCK-4 and CCK-8s in the rat brain tissue.