Purification and characterization of guinea-pig chorionic gonadotrophin

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Abstract
Summary. A human chorionic gonadotrophin-like protein (GF-1, 1·0 g) from the placentae of 50 guinea-pigs killed at Day 26 of gestation was purified by pH and ammonium salt fractionation followed by column chromatography on DEAE-Sephadex and filtration on Sephadex G-100. Relative to the Second International hCG standard (MRC 61/6) GF-1 had an immunological potency of 21 000 i.u./mg as measured in a specific hCG-β radioimmunoassay and, using the ovarian ascorbic acid depletion assay, an apparent biological potency of 24 064 i.u./mg. Isoelectric focussing yielded 6 bands between pH 4·4 and 5·7 and the material comprised two non-covalently linked subunits. The Stokes' radii were 3·40 nm for the native preparation, and 2·38 nm and 3·15 nm for GF-1-α and GF-1-β subunits respectively. The guinea-pig placenta therefore produces a chorionic gonadotrophin which on purification has physicochemical, biological and immunological properties similar to those of hCG.