The Molecular Nature of Cholecystokinin in Plasma: An in vivo Immunosorption Study in Rabbits

Abstract

Rehfeld JF. The molecular nature of cholecystokinin in plasma. An in vivo immunosorption study in rabbits. Scand J Gastroenterol 1994;29:110-121.

The nature of cholecystokinin (CCK) in rabbit plasma was examined by means of a novel in vivo immunosorption procedure. Cholecystokinin (CCK) antibodies in 11 rabbit antisera were denatured, and the released peptides characterized by size and reversed-phase chromatography. Five of six antisera specific for the COOH terminus of CCK contained substantial amounts of CCK-22- and CCK-8-like peptides and small amounts of CCK-33-like peptides (range, 120 to 1140nmol/l antiserum). In contrast, neither antisera for the NH₂-terminus and mid-sequence of porcine CCK-33 nor antisera against the glycine-extended COOH terminus released CCK peptides. Postprandial acidified plasma from non-immunized rabbits concentrated in vitro also contained mainly CCK-22- and -8-like peptides, whereas extracts of rabbit duodenum and jejunum in addition contained forms resembling CCK-58, -39, and/or -33. The results show that mainly small molecular forms of CCK circulate in rabbits, and that NH₂-terminal and mid-sequences of porcine and human CCK-33 differ from those of rabbit CCK-33. The results support the contention that plasma in most mammals contains small molecular forms of CCK.

Key Words:

• Hormone heterogeneity
• immunoanalysis
• posttranslational processing