Unmasking by neuraminidase of specific chorionic gonadotrophin binding activity of human placental syncytiotrophoblast.
Purified human placental syncytiotrophoblast consistently failed to bind specifically to 125I-labelled hCG. Treatment of the syncytiotrophoblast with neuraminidase resulted in the ability to bind 125I-labelled hCG that was displaceable by excess of unlabelled hCG. Neuraminidase treatment removed 73.8% of the total neuraminic acid of syncytiotrophoblast. The specific binding of 125I-labelled hCG increased linearly with increasing amount of neuraminidase-treated syncytiotrophoblast, was saturable and had a Ka = 1.6 x 10(7) M-1. Excess of GH, prolactin, placental lactogen or insulin did not inhibit the binding, whereas LH did so completely and FSH partly.
D006063:Chorionic Gonadotropin / Q000378:metabolism*; D046508:Culture Techniques; D005260:Female; D006801:Humans; D007700:Kinetics; D009439:Neuraminidase / Q000494:pharmacology*; D011247:Pregnancy; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011974:Receptors, LH; D014327:Trophoblasts / Q000187:drug effects / Q000378:metabolism*
D006063:Chorionic Gonadotropin; D011956:Receptors, Cell Surface; D011974:Receptors, LH; D009439:Neuraminidase