Evaluation of a radioimmunoassay for cholecystokinin in human plasma.
A sensitive and specific radioimmunoassay for cholecystokinin (CCK) in human plasma was developed using an antiserum specific for sequence 26-29 of CCK-33 and 125I-Bolton-Hunter labelled sulphated CCK-8 as tracer. Plasma was extracted in 96% ethanol before assay. The detection limit of the assay was 0.3 pmol/l. CCK-33 and CCK-8 were stable in plasma at 0 degree C for at least 3 h, but CCK-8 was degraded at 21 degrees C. The trypsin inhibitor, aprotinin, did not affect the degradation of CCK-8, while the aminopeptidase inhibitor, bestatin, had a significant inhibitory effect. The basal plasma concentration of CCK in 44 normal subjects was 1.6 +/- 0.2 pmol/l, ranging from undetectable (less than 0.3 pmol/l) to 4.4 pmol/l. After the ingestion of a mixed meal in seven normal subjects, concentrations of plasma CCK rose from 2.0 +/- 0.2 to 7.4 +/- 0.7 pmol/l. Diurnal registration in nine people showed similar increments after each meal. The validity of the assay was further substantiated by a strong correlation between CCK measurements of identical samples with other CCK specific antisera.
D000626:Aminopeptidases / Q000037:antagonists & inhibitors; D007611:Aprotinin / Q000494:pharmacology; D002766:Cholecystokinin / Q000097:blood*; D002940:Circadian Rhythm; D005502:Food; D006801:Humans; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D011863:Radioimmunoassay / Q000379:methods
D002766:Cholecystokinin; D007611:Aprotinin; D000626:Aminopeptidases; D007930:Leucine; C012211:ubenimex