Assay Characteristics of Tannate Complexes of Human Chorionic Gonadotropin

Abstract

Tannates of human chorionic gonadotropin (HCG) were assayed by the ventral prostate weight (VPW) assay and by the ovarian ascorbic acid depletion (OAAD) assay. Assays were also performed by injecting single doses of tannated and untannated HCG and determining the magnitude of the response at various intervals. It was found that tannation increased the potency of HCG 3.3-fold in the VPW assay and 1.8-fold in the OAAD assay. The responses obtained with single doses were also greater for the tannate than for the free HCG. The increased potency of the tannated HCG in both assay systems suggests that two factors may be operative–delayed metabolism and a direct chemical effect of tannation on the HCG molecule. (Endocrinology76: 499,1965)