Effect of removal of carbohydrate residues upon the half life and in vivo biological activity of human chorionic gonadotropin.

The effect of progressive enzymatic removal of various carbohydrates on the half life (T 1/2) and biologic activity in vivo of hCG was studied in rats. The cleavage of carbohydrates such as galactose, glucosamine and mannose, in addition to sialic acid, reduced the T 1/2 from 60--90 for native hCG to less than 3 minutes. The hCG derivatives had no inherent ability to cause ovulation, but in PMSG, Nembutal-treated immature rats, the hCG derivatives with carbohydrate residues internal to sialic acid removed blocked the stimulatory effect of native hCG upon ovulation.