Determination of cholecystokinin tetrapeptide and cholecystokinin octapeptide sulfate in different rat brain regions by high-pressure liquid chromatography with electrochemical detection

A method for the determination of cholecystokinins in biological material, based on high-pressure liquid chromatography with direct electrochemical detection (HPLC-EC), is described. Using this method, the levels of cholecystokinin tetrapeptide and octapeptide sulfate in rat brain cortex, hippocampus, striatum, and brain stem were measured and found to be comparable to those reported using radioimmunoassay methods. We show that HPLC-EC is sensitive enough to accurately determine neuropeptides in brain tissue without prior derivatization and is therefore, due to its simplicity, an attractive alternative to existing methods.     

Large and small forms of cholecystokinin in human plasma: measurement using high pressure liquid chromatography and radioimmunoassay

Defining the role of cholecystokinin (CCK) in gut physiology and disease has proved difficult because of problems with development of radioimmunoassays and because CCK exists in several different molecular forms which have different biological actions. In order to measure small (8 amino acid residues, CCK 8) and large (33 and 39 residues) forms of CCK in plasma we have developed high pressure liquid chromatographic (HPLC) fractionation of plasma prior to radioimmunoassay. Fasting plasma CCK 8 and CCK $\text{33}\text{39}$ levels were usually undetectable (< 3 and < 6 pmol/1, respectively). After a liquid fat meal both CCK 8 and CCK $\text{33}\text{39}$ levels were significantly elevated at 5 min (11.3±3.3 and 11.6±2.6 pmol/1, respectively). Peak CCK 8 levels occurred at 30 min (15.0±4.4 pmol/1) while peak CCK $\text{33}\text{39}$ levels occurred at 120 min (16.7±4.9 pmol/1. Total CCK levels showed a biphasic response to the meal. These CCK 8 and CCK $\text{33}\text{39}$ responses to oral fat are consistent with a role for these hormones in the regulation of gallbladder emptying and pancreatic secretion.