Radioimmunoassay of cholecystokinin in plasma.
A sensitive and specific radioimmunoassay for cholecystokinin (CCK) has been developed. Synthetic unsulfated carboxy-terminal fragment, CCK-8, was radioiodinated by the conventional Chloramine-T method. Antibodies were raised against sulfated CCK-8 covalently coupled to bovine thyroglobulin via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. By purification, highly immunoreactive 125I-labeled CCK-8 was obtained. The antiserum was highly avid, and plasma could be assayed directly. The detection limit of the assay was 5 pmol of sulfated CCK-8 per liter. The assay measured fragments CCK-8, CCK-33, and CCK-39 with equimolar potency. CCK-4, gastrin, and vasoactive intestinal polypeptide were not detected, even at higher concentrations. The concentration of CCK, as the sum of these CCK peptides, in plasma during fasting was low (10.5 +/- 2.1 pmol/L, mean +/- SEM) but still detectable in all normal subjects examined (range, 6.4-20.1 pmol/L). After ingestion of a test meal, CCK in plasma increased rapidly, peaking at 41.3 (SEM 5.7) pmol/L at 40 min and remaining high for 3 h after the meal. This supports the concept that CCK has important roles in digestion and absorption.
Ohgo
S
S
Department of Internal Medicine, Miyazaki Medical College, Japan.
Takemura
J
J
Oki
Y
Y
Nishizono
F
F
Ishikawa
E
E
Yoshimi
T
T
Yamamura
T
T
Seino
Y
Y
Matsukura
S
S
D000328:Adult; D002766:Cholecystokinin / Q000097:blood*; D005502:Food; D006801:Humans; D008297:Male; D011863:Radioimmunoassay; D012016:Reference Values; D012844:Sincalide / Q000097:blood
D002766:Cholecystokinin; D012844:Sincalide