Immunoreactive chorionic gonadotropin (CG) produced by human choriocarcinoma cells in culture was compared with CG from urinary sources by polyacrylamide gel electrophoresis (PAGE) and isoelectric focusing in polyacrylamide gel (IFPA). CG from both sources had the same molecular size in PAGE operative at pH 10.2 and 5.5. However, PAGE revealed heterogeneity with regard to molecular net charge for both hormone preparations. Two species of CG characterized by pis of 3 and 4.5 were re vealed in the tissue culture medium on examination by IFPA. Digestion of both species with neuraminidase produced a single immunoreactive CG with pi of 6. Heterogeneity of CG with regard to net charge and isoelectric point may reflect variable completion of the carbohydrate portion of these molecules at the cell of origin.
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