title: Novel opioid peptides endomorphin-1 and endomorphin-2 are present in mammalian immune tissues.
abstract: Endomorphin (EM)-1 and EM-2 are opioid tetrapeptides, reported within the central nervous system, which have very high specificity and affinity for the mu-opioid receptor. We have used newly developed and well-characterised radioimmunoassays (RIAs) in combination with reversed-phase high-performance liquid chromatography (HPLC) to detect EM-1 and EM-2 immunoreactivity (ir) in rat immune tissues. Endomorphins were detectable in extracts of rat spleen (total EM-1-ir/spleen: 440+/-73 pg, mean+/-SEM, a=group of eight rats; EM-2-ir: 150+/-12 pg) and thymus (EM-1-ir: 152+/-18 pg, mean+/-SEM n=8; EM-2-ir: 156+/-28 pg). EM-2-ir was detectable in extracts of human spleen (338+/-196 pg/g tissue, n=3). Multiple peaks of EM-1-ir and EM-2-ir were observed in rat spleen and thymus extracts, and multiple peaks of EM-2-ir were observed in extracts of human spleen, following reversed-phase HPLC and RIAs. This is the first report of endomorphin immunoreactivity in tissues of the rat and human immune systems.
authors.affiliation: Division of Medicine, University of Bristol, Marlborough Street, Bristol, UK. david.jessop@bris.ac.uk
authors.forename: D S
authors.initials: DS
authors.lastname: Jessop
authors.forename: G N
authors.initials: GN
authors.lastname: Major
authors.forename: T L
authors.initials: TL
authors.lastname: Coventry
authors.forename: S J
authors.initials: SJ
authors.lastname: Kaye
authors.forename: A J
authors.initials: AJ
authors.lastname: Fulford
authors.forename: M S
authors.initials: MS
authors.lastname: Harbuz
authors.forename: F M
authors.initials: FM
authors.lastname: De Bree
mesh_terms: D000328:Adult; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003429:Cross Reactions; D005260:Female; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D007107:Immune System / Q000737:chemistry*; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides / Q000032:analysis*; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D013154:Spleen / Q000737:chemistry; D013950:Thymus Gland / Q000737:chemistry; D014020:Tissue Extracts / Q000737:chemistry
chemical_list: D007106:Immune Sera; D009842:Oligopeptides; D014020:Tissue Extracts; C105293:endomorphin 1; C105294:endomorphin 2