title: Methodological aspects of rat beta-endorphin analysis-influence of diurnal variation.
abstract: Beta-endorphin radioimmunoassays (RIAs) are widely performed following physical, emotional and environmental challenges in the rat. In the literature, a wide range of techniques have been described, but in the present study, we have focused on methodological aspects of beta-endorphin RIAs, investigating various characteristics of human and rat specific antibodies. Initial studies verified that the RIA outcome was not appropriate when using non-species compatible components. Novel rat beta-endorphin antibodies, r 4114 and r 4268, were raised in rabbits and characterised in terms of specificity, avidity and titer. Both of the new antisera showed 68.1% cross-reactivity with human beta-endorphin. The ED50 was 50+/-8 pmol/l, and the mean ED80 was 17 pmol/l for r 4268 but three-fold higher for r 4114. The intra-assay coefficient of variation (CV) was 7% at 100 pmol/l and the inter-assay CV was 10% at the same level for r 4268 and similar for r 4114. Using this novel rat beta-endorphin RIA for analyses of diurnal influence and removal from the Animal House cage, no significant changes were observed in either the hypothalamus or peri-aqueductal grey regions. These results suggest that rat beta-endorphin concentrations in these brain areas are not affected by order of removal or diurnal variation.
authors.affiliation: Peptide Laboratory, Section of Medical Rehabilitation, Department of Surgical Sciences, Sweden. Anja.Finn@haninge.mail.telia.com
authors.forename: Anja
authors.initials: A
authors.lastname: Finn
authors.forename: Susanne Froelich
authors.initials: SF
authors.lastname: Fabre
authors.forename: Per M
authors.initials: PM
authors.lastname: Hellström
authors.forename: Stefan
authors.initials: S
authors.lastname: Brené
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology*; D002940:Circadian Rhythm; D003429:Cross Reactions; D006801:Humans; D007031:Hypothalamus / Q000737:chemistry*; D008297:Male; D008969:Molecular Sequence Data; D011863:Radioimmunoassay / Q000379:methods*; D051381:Rats; D011917:Rats, Inbred Lew; D013315:Stress, Psychological / Q000378:metabolism; D001615:beta-Endorphin / Q000032:analysis* / Q000276:immunology
chemical_list: D000906:Antibodies; D001615:beta-Endorphin