title: Radio-immunoassay of endothelin in human plasma.
abstract: Endothelin (ET) is a newly described endothelium-derived 21-amino-acid peptide with potent vasoconstrictive properties. The present study describes a radio-immunoassay utilizing an antibody without cross-reactivity with big endothelin, produced after immunization of rabbits with endothelin-1 (ET-1). Measurement of endothelin in human plasma was performed after prior extraction on Sep-pak C18 cartridges. Recovery of unlabelled endothelin-1 added to human plasma (3.5 pg ml-1) was 84.8 +/- 11.1% (mean +/- SD, n = 12). The minimum detectable level in plasma was 50 fmol 1-1. High-pressure liquid chromatography on reverse-phase C18 column established that the measured irET eluted identically to ET-1. The concentration of irET in plasma from healthy control subjects was 1.11 +/- 0.2 pmol-1 (mean +/- SD, n = 30). Agarose electrophoresis of plasma with [125I]-ET-1 indicated a reversible binding to albumin. It is concluded that ET-1 is present in measurable amounts in human plasma. It is suggested that ET-1 in plasma is associated with albumin. The importance of an adequate extraction procedure is stressed.
authors.affiliation: Department of Nephrology and Medicine C, Skejby Hospital, Aarhus C, Denmark.
authors.forename: S S
authors.initials: SS
authors.lastname: Sørensen
mesh_terms: D001345:Autoradiography; D002851:Chromatography, High Pressure Liquid; D004586:Electrophoresis; D016232:Endothelins / Q000097:blood* / Q000302:isolation & purification; D006801:Humans; D011863:Radioimmunoassay; D012016:Reference Values; D012680:Sensitivity and Specificity
chemical_list: D016232:Endothelins