1993 年 22 巻 4 号 p. 230-237
A fluorescent enzyme immunoassay (EIA) for measurement of cholecystokinin (CCK) in human plasma was developed. An alkaline phosphatase (Alp)-labeled CCK-33 conjugate was used as a tracer in the EIA. The bound and free fractions were separated with the use of a second antibody (goat anti-rabbit IgG antibody) coated to beads. The Alp-labeled CCK-33 conjugate bound to beads was measured flurophotometrically using 4-methylumbelliferyl phosphate as a substrate. The range of measurement and the fifty percent inhibitory concentration (IC50) for CCK-8 were 0.4 to 100fmol/assay and 5.3fmol/assay, respectively. The sensitivity of this assay was 5 times higher than that using Alp-labeled CCK-8 and radioimmunoassay (RIA) using 125I-CCK-39 as a tracer. The measurement of CCK in plasma samples required pretreatment by immuno-affinity columm extraction of CCK in order to achieve separation from interfering substances. The rate of recovery of CCK-8 using the immuno-affinity column was 97.4±14.8% (n=36). The coefficient of correlation between values of CCK plasma concentration obtained by the fluorescent EIA and RIA was 0.940 (n=71). The plasma CCK concentration of normal subjects and patients with various diseases could accurately by measured with the EIA we have proposed.
