Inactivation of Human Chorionic Gonadotropin Extracted from Chorionic Tissue and Serum by Neuraminidase

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Human chorionic gonadotropin was extracted from serum and chorionic tissue of the first and third trimester. Their stability of LH activity to neuraminidase incubation and sialic acid content were studied. Biological activity was determined by OAAD method. The data were compared with those of NIH-LH and urinary HCG. Gonadotropins which were extracted from chorionic tissue and serum lost about 80% of their biological activity when incubated for two hours with neuraminidase. An exception was the extract of the third trimester's chorionic tissue which showed significantly large residual activity. NIH-LH was stable against neuraminidase treatment and only 10% loss of biological activity was observed after two hours incubation. On the other hand, the loss of HCG's biological activity was approximately 75% after one hour and purified HCG (5917IU/mg) was inactivated 90% within one hour. Sialic acid content of extracts obtained from chorionic tissue and serum were in a range of 0.3-0.4%, but the extract of the third trimester's chorionic tissue was known to have significantly low sialic acid. NIH-LH-S14 had 1.1% of sialic acid, urinary HCG had 0.69% and purified HCG had 5.7%.