title: Distribution and characterization of the opioid octapeptide met5-enkephalin-arg6-gly7-leu8 in the gastrointestinal tract of the rat.
abstract: The distribution and characterization of the opioid octapeptide met5-enkephalin-arg6-gly7-leu8 (met5-enk-arg6-gly7-leu8) within the gastrointestinal tract of the rat has been determined by immunohistochemistry and radioimmunoassay by use of a newly developed antibody to met5-enk-arg6-gly7-leu8. With both techniques, met5-enk-arg6-gly7-leu8-immunoreactivity (met5-enk-arg6-gly7-leu8-IR) was detected in all regions of the gastrointestinal (GI) tract except the esophagus. The highest concentration of immunoreactive met5-enk-arg6-gly7-leu8 was observed in the colon, while intermediate concentrations were found in the stomach, duodenum, jejunum, and ileum. Immunostained somata were observed chiefly in the myenteric plexus; immunostained processes were present primarily in the myenteric plexus and the circular muscle layer. This distribution pattern is similar to that previously observed with antiserum to met5-enkephalin-arg6-phe7 (met5-enk-arg6-phe7). Chromatographic analysis of met5-enk-arg6-gly7-leu8-immunoreactive peptides extracted from the GI tract revealed the presence of an immunoreactive peptide of high molecular weight which accounted for approximately three-quarters of met5-enk-arg6-gly7-leu8-IR in both stomach and colon. These findings suggest a role for peptides related to the octapeptide met5-enk-arg6-gly7-leu8 in the regulation of GI function.
mesh_terms: D000818:Animals; D000906:Antibodies; D000918:Antibody Specificity; D001369:Axons / Q000032:analysis; D002850:Chromatography, Gel; D004064:Digestive System / Q000032:analysis* / Q000276:immunology; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000032:analysis / Q000276:immunology; D005455:Fluorescent Antibody Technique; D006651:Histocytochemistry; D008297:Male; D008970:Molecular Weight; D009474:Neurons / Q000032:analysis; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000906:Antibodies; D004744:Enkephalin, Methionine; C033453:enkephalin-Met, Arg(6)-Gly(7)-Leu(8)-