title: Evidence for a nonspecific factor interfering in the radioimmunoassay of somatoliberin-like immunoreactivity in human seminal plasma.
abstract: In the present study we investigated the nature of somatoliberin-like immunoreactivity in human seminal plasma. In unextracted seminal plasma, somatoliberin-like immunoreactivity represented 3.8 micrograms/l somatoliberin, with a dilution curve that ran almost completely parallel to that of synthetic somatoliberin standard. After extraction by adsorption on hydrophobic C 18 Sep-pak cartridges or immunoaffinity chromatography, no somatoliberin-like immunoreactivity in seminal plasma could be detected. After gel permeation chromatography on a Sephadex G-50 fine column, all somatoliberin-like immunoreactivity of unextracted seminal plasma was recovered at the void volume of the column. When equal volumes of unextracted seminal plasma and radioiodinated somatoliberin were coincubated for two days at 4 degrees C, gel chromatography revealed the disappearance of the normal [125I]somatoliberin peak, replaced by a new peak eluting shortly after the total volume of the column. When unextracted seminal plasma was heated at 90 degrees C for 10 min or submitted to ultrafiltration, the interfering factor was no longer detectable. Our data show that enzymic degradation of radioiodinated somatoliberin led to misleadingly high concentrations of somatoliberin-like immunoreactivity in seminal plasma. These phenomena should therefore be considered when performing radioimmunoassays of short chain peptides in biological fluids.
mesh_terms: D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D013007:Growth Hormone-Releasing Hormone / Q000032:analysis*; D006801:Humans; D008297:Male; D011863:Radioimmunoassay; D012661:Semen / Q000032:analysis*
chemical_list: D013007:Growth Hormone-Releasing Hormone