Plasma cholecystokinin and neurotensin after an ordinary meal in humans. A prolonged time study

Background/Aim. - Ingestion of a meal causes the release of cholecystokinin and neurotensin into the circulation, but little is known about the duration of this release. Methods. - Six healthy volunteers were studied. Blood samples for cholecystokinin, neurotensin and gastrin assessment were drawn before and after consumption of a typical Italian lunch. Postprandial samples were obtained every hour for a total of 10 hours. All peptides were measured using previously validated radioimmunoassays. Results. - Ingestion of the meal caused a prompt and significant increase in plasma levels of all three peptides. Cholecystokinin remained elevated for about 7 hours and then tended to return towards basal values, whereas the increase of neurotensin persisted for the entire period of the study (10 hours). Gastrin remained elevated for about 5 hours and then declined. The integrated CCK and gastrin responses during the initial postprandial hours were greater than those in the late hours, whereas the integrated neurotensin response during the initial hours was lower than that in the late hours. Conclusions. - The results indicate that, after an ordinary meal, cholecystokinin is released into the circulation for about 7 hours, much longer than previously reported (3-4 hours). The release of neurotensin begins soon after the meal and persists even longer, for at least 10 hours. Possible physiological implications of these findings are discussed.