Submitted on December 11, 2002
Accepted on April 3, 2003
CCK-58 is the only detectable endocrine form of cholecystokinin in rat
Joseph R. Reeve, Jr.1*, Gary M. Green2, Peter Chew1, Viktor E. Eysselein3, and David A. Keire1
1 VA GLHS / Digestive Diseases Division, CURE Center for Digestive Disease Research / UCLA School of Medicine, Los Angeles, CA, USA
2 Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
3 Division of Gastroenterology, Harbor UCLA Medical Center, Torrance, CA, USA
* To whom correspondence should be addressed. E-mail: jreeve{at}ucla.edu.
CCK-58 differs from CCK-8 in patterns of expression of pancreatic secretion of fluid and amylase, and gallbladder contraction. These differences have physiological relevance only if CCK-58 release is stimulated by nutrients entering the intestine and if CCK-58 circulates in sizeable amounts. In this study, we report that when radiolabeled CCK-58 is added to rat blood and plasma is formed, there is extensive loss and degradation of the radioactive peptide. Therefore, a new method was designed to minimize loss and degradation of this label. This method recovered more than 85% of the label with no detectable degradation. Furthermore, the optimized method recovered all exogenous cholecystokinin molecular forms in greater than 80% yields. Blood from fasted rats and rats where cholecystokinin release was stimulated by trypsin inhibitor, camostat contained only CCK-58 (3.5 ± 0.5 fmol/mL and 17 ± 1.5 fmol/mL, respectively). Because CCK-58 predominates in the blood this molecular form should be used in studies on the physiology and pathophysiology of cholecystokinin.
