Measurement of Unconjugated 17β-Estradiol in Plasma by Competitive Protein Binding

[摘要] A sensitive and quick competitive protein-binding method is described for measuring unconjugated 17β-estradiol in the plasma of women and sheep. One-milliliter aliquots of plasma, with tritiated estradiol standard added as an index to recovery, are extracted with methylene chloride. Plasma extracts of 17β-estradiol are purified and isolated by adsorption on G-15 Sephadex. The purification procedure does not separate 17α-estradiol from 17β-estradiol, but there is less than 0.05% cross reaction in the binding assay. Recovery of 17β-estradiol is 50-55%. Plasma from human twin pregnancies is used as a source of binding protein in the displacement assay. Free 17βestradiol is separated from bound estradiol by ammonium sulfate precipitation. The standard curve lies in the range 0-200 pg, with less than 4% variation between duplicate points. Sensitivity of the displacement curve at zero value is 2 pg. Values for method blanks are 9.8 ± 1.3 pg/ml (SD) (n = 28). Variation between replicates, including between-assay variation, is less than 10%.

[学科分类] 过敏症与临床免疫学