AJP - Gastrointestinal and Liver Physiology, Vol 273, Issue 3 754-G758, Copyright © 1997 by American Physiological Society

ARTICLES

An amino-terminal fragment of LCRF, LCRF-(1-35), has the same activity as the natural peptide

A. W. Spannagel, J. R. Reeve Jr, R. A. Liddle, D. Guan and G. M. Green
Department of Physiology, University of Texas Health Science Center, San Antonio 78284-7756, USA.

A cholecystokinin (CCK)-releasing peptide, luminal CCK-releasing factor (LCRF), has been purified from rat jejunal secretion. Amino acid analysis and mass spectral analysis showed that the purified peptide is composed of 70-75 amino acid residues and has a mass of 8,136 Da. Microsequence analysis of LCRF yielded an amino acid sequence for the amino-terminal 41 residues. To determine the biologically active region of the molecule, a peptide was synthesized consisting of the amino-terminal 35 amino acids of LCRF. In this study, intraduodenal infusion of LCRF-(1-35) significantly stimulated pancreatic secretion in conscious rats. The dose-response curves to LCRF-(1-35) and to monitor peptide were similar and biphasic, with higher doses producing submaximal pancreatic secretory responses. The CCK-A receptor antagonist MK-329 abolished the pancreatic secretory response to intraduodenally infused LCRF-(1-35). These results demonstrate that LCRF biological activity is contained within the amino-terminal 35-amino acid portion of LCRF, and this fragment may be useful for investigating the role of LCRF in gastrointestinal function.

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