CHARACTERIZATION OF THE HUMAN CHORIONIC GONADOTROPHIN FRACTIONS IN PREGNANCY URINE

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Abstract
The human chorionic gonadotropin (hCG) preparation (approximately 3000 IU/mg) from pooled pregnancy urine has been fractionated using anion-exchange and gel exclusion chromatography. The various fractions, many of which were heterogeneous, were assayed using radioimmunoassay (RIA) and a testicular radio-receptor assay (RRA). Three fractions were obtained with potencies of 9000-20,000 IU/mg; 5 fractions were characterized by potencies of 1000-6000 IU/mg; and 4 fractions exhibited low potencies (< 500 IU/mg). A linear relationship between RRA and RIA potency (P) existed for the various fractions: 1n(PRRA) = 1.14 1n(PRIA) - 1.67. The major fractions, which exhibited various potencies, were further characterized by amino acid and carbohydrate analysis. Urine was collected from an individual at various times of gestation, and the hCG fraction was concentrated by benzoic acid and ethanol precipitation. Ion-exchange chromatography of the hCG fraction yielded multiple immunoreactive components throughout pregnancy; thus the observed heterogeneity in the commercial preparation does not appear to result from processing pooled urine from numerous donors. Heterogeneity was observed in an individual donor whose urine was not treated with the benzoic acid and alcohol fractionation scheme. Individual urinary hCG is heterogenous, and this does not appear to reflect isolation artefacts.