Plasma cholecystokinin responses after ingestion of liquid meal and intraduodenal infusion of fat, amino acids, or hydrochloric acid in man: analysis with region specific radioimmunoassay.

A highly sensitive and precise radioimmunoassay system for plasma cholecystokinin (CCK) was developed with the anti-CCK-8 specific antiserum which raised against N-terminal amino acids residue of sulfated CCK-8 and reacted with CCK-8, CCK-33, and CCK-39 but not with gastrin and its related peptides. Mean concentration of the fasting plasma CCK determined with this method using CCK-8 as standard was 12.9 +/- 5.9 pg/ml in normal subjects (n = 26), and in patients with hepatic cirrhosis it was significantly higher (36.7 +/- 16.9 pg/ml, n = 9, p less than 0.01) than in normal subjects. In six young healthy volunteers, intraduodenal infusion of fat caused a significant increase (p less than 0.05) of plasma CCK from a basal level of 8.0 pg/ml to a peak of 43.0 +/- 12.0 pg/ml at 20 min after starting of infusion. In the same subjects, a significant increase of plasma CCK was also observed by amino acids infusion, but no elevation of plasma CCK level was found during intraduodenal acidification.