Inhibition of the thyroid adenylate cyclase response to thyroid-stimulating immunoglobulin G by crude and asialo-human chorionic gonadotropin.

Abstract

In view of previous findings that crude, and particularly desialylated, forms of hCG are capable of inhibiting the increase in cAMP concentrations induced in human thyroid membranes by TSH, we have conducted experiments to determine whether hCG is capable of inhibiting the response to the stimulatory immunoglobulins of Graves' disease (G-IgG). Preparations studied were crude hCG (hCG-c; 2500 IU/mg), pure hCG (hCG-p; 13,400 IU/mg), and desialylated derivatives thereof. Slices of normal human thyroid were employed as the target tissue, and an increase in the tissue cAMP concentration was used as the index of response. G-IgG were prepared from the pooled sera of patients with untreated Graves'disease by means of chromatography on columns of staphylococcal protein A-Sepharose. Up to a concentration of 20 mg/ml, increasing concentrations of G-IgG increased tissue cAMP concentrations in a dose-dependent manner. When 10 mg G-IgG and 1.2 mg hCG-c were incubated together, a highly significant inhibition of the res...