Effect of Removal of Carbohydrate Residues upon the Half Life and in Vivo Biological Activity of Human Chorionic Gondadotropin
It has been previously shown (1, 2) that progressive removal of sialic acid from human chorionic gonadotropin (hCG) decreases the half life, as well as the in vivo biologic activity of the gonadotropin. The effect of removing sugar residues internal to sialic acid upon the half life and biologic activity of hCG has not yet been examined. In vitro studies, using isolated porcine (3) and monkey (4) granulosa cells, indicate that the successive removal of sugar residues internal to sialic acid from native hCG lead to a diminution in ability to stimulate cyclic AMP accumulation and progesterone secretion. The ability to inhibit binding of iodinated hCG to porcine granulosa cells was not appreciably altered provided the hCG derivative was added prior to the tracer molecule. In both monkey and pig granulosa cells the hCG derivatives with sugar residues internal to sialic acid removed, acted as competitive inhibitors of hCG action. In order to examine whether hCG derivatives have biologic activity in vivo and whether they have the ability to inhibit LH and hCG action in vivo their possible interfering effect on ovulation in prepuberal female rats primed with pregnant mare serum gonadotropin was studied. In addition, the half life of the hCG derivatives was examined in adult female rats.
KeywordsHalf Life Sialic Acid Granulosa Cell Corpus Luteum Carbohydrate Residue
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