Subunits of human chorionic gonadotrophin: an immunochemical study

The α and β subunits of HCG were prepared by urea-treatment of the hormone and isolated by DEAE-Sephadex A-25 chromatography. Further purification of the subunits was achieved by gel filtration on Sephadex G-100.

Partial chemico-physical characterization confirmed the non-identity of the HCG subunits, as previously reported by several investigators.

A radioimmunoassay (RIA) system based on 125I-HCG-β + anti-HCG-β serum was used to study the antigenic similarities between HCG, HCG-α and -β, human pituitary LH, urinary LH and FSH. The highest cross-reactivity was found for HCG, followed by HCG-α, LH and FSH.

The specificity of the above mentioned RIA system was increased by absorbing the anti-HCG-β serum with HCG-α. Because of the ability of this absorbed antiserum to discriminate between HCG and LH, a study was carried out to detect specifically HCG in urine in spite of the presence of physiological amounts of LH.