DETERMINATION OF PLASMA ET-1 BY RIA - RISKS AND LIMITATIONS

Plasma concentrations of the vasoconstrictor peptide endothelin-1 (ET- 1) were determined in nonobese healthy subjects as well as in unspecif ied patients using three different commercially available radioimmunoa ssays (RIAs) and the respective recommended prepurification procedures . Depending on the antibody and extraction procedure applied different ET-1 concentrations were measured in identical plasma samples. Thus, this study clearly documents that ET-1 concentrations measured in plas ma samples represent apparent concentrations which have to be interpre ted with caution.