Effects of cholecystokinin octapeptide on the pancreatic exocrine secretion in the pig

Abstract

In conscious pigs, intravenous infusion of serial doses of cholecystokinin octapeptide (CCK8; 2.9–232.3 pmol∙kg−l∙min−1) upon a background of secretin resulted in a linear increase of plasma CCK-like immunoreactivity (CCK-LI) concentration and evoked a dose-related increase of pancreatic volume and bicarbonate and protein outputs. The threshold plasma CCK-LI concentration for significant pancreatic response was 103.8 ± 10.2 pM using a CCK8 dose of 8.8 pmol∙kg−1∙min−1. The maximum pancreatic response was observed for a plasma CCK-LI level of 498.0 ± 15.3 pM using 77.2 pmol CCK8∙kg−1∙min−1. In anesthetized pigs, the threshold plasma CCK-LI concentration for pancreatic response was 1500 pM (actual CCK8 dose of 60.3 pmol∙kg−1∙min−1). The physiological relevance of this finding was assessed by comparing the food-induced increase of pancreatic secretion with that of plasma CCK-LI. Food ingestion was followed by a sharp pancreatic response and by a progressive increase of plasma CCK-LI to a peak increment of about 15 pM. Gel chromatography of portal and peripheral plasma from fed animals revealed three major peaks in the volumes of CCK33/39 and CCK8, and in a volume intermediate between CCK33/39 and CCK8. An additional minor component eluted ahead of CCK33/39. CCK8, which is one of the CCK components released after food intake, appears to be a fairly weak pancreatic stimulant in pigs.Key words: cholecystokinin, pig, pancreas, secretion.