CHARACTERISTIC AND LOCALIZATION OF THE MONITOR PEPTIDE RECEPTOR

The monitor peptide receptor in the small intestine was investigated. The receptor is on the intestinal mucosal cells Biochem. J., in press !. The specific binding of the I-125 labeled monitor peptide to disper sed rat small intestinal cells was inhibited by treatment with p-tolue nsulfonyl-L-lysine chloromethyl ketone (TLCK), an affinity labeling re agent for trypsin. Soybean trypsin inhibitor (SBTI) did not inhibit th e binding. Analysis with reduced SDS electrophoresis-autoradiography i ndicated that an affinity-cross-linked complex of the I-125 labeled mo nitor peptide and the receptor was abolished by the TLCK treatment but was not affected by the presence of SBTI. Histochemical studies found a predominatnt binding of I-125 labeled monitor peptide on cholecysto kinin (CCK)-immunoreactive cells in tissue sections of the rat upper i ntestine. The result suggests that the monitor peptide receptor is on the surface of CCK-producing cells.