Plasma levels of cholecystokinin (CCK-8 and CCK-33-39) in response to feeding and during pregnancy in dogs.

A method for measuring plasma cholecystokinin (CCK) levels in dogs which enables separate determination of small (CCK-8) and large (CCK-33-39) molecular forms by using reversed-phase high-performance liquid chromatography before radioimmunoassay is presented. Basal levels of CCK averaged 1.8 pM and rose to 4.6 pM 60 min after feeding. The ratio between small and large molecular forms was 1:1 in basal samples but 3:1 and 1:2 in samples collected 10 and 60 min after feeding, respectively. In pregnant dogs basal CCK levels were significantly increased (5 pM) and equally distributed for CCK-8 and CCK-33-39.