Adenylate Cyclase Activity and the Accumulation and Release of Adenosine 3',5'-Monophosphate in Normal Human Thyroid Tissue Slice Preparations: Responses to Thyrotropin and Thyroid-Stimulating Antibodies*

Publisher Website
Google Scholar
Abstract
The cAMP response to TSH was investigated in slice preparations of normal human thyroid tissue maintained under in vitro conditions. Dose-response relationships for tissue obtained from differnet thyroid glands were assessed, and the sensitivity and precision of this system were compared with the adenylate cyclase response to TSH in plasma membrane preparations derived from similar tissue. The effect of thyroid-stimulating antibodies (TSAb) on the thyroid slice cAMP response was investigated. After an incubation period of 120 min, 58% of a series of 43 IgG fractions prepared from the sera of Graves'' disease patients significantly elevated the slice level of cAMP when assayed in triplicate at a level of 5 mg/ml. From a total of 22 preparations of IgG from untreated thyrotoxic patients, 11 (50%) stimulated the accumulation of cAMP in thyroid slices. Six out of a group of 8 patients with Graves'' ophthalmopathy had demonstrable TSAb activity. After the initiation of antithyroid therapy with carbimazole, IgG preparations from 5 out of a group of 8 patients were without detectable TSAb activity. However, cAMP accumulation was stimulated by all 5 of a group of IgG preparations from previously thyrotoxic patients who had relapsed upon cessation of antithyroid therapy. The elevated cAMP levels in tissue slices in response to either TSH or TSAb were accompanied by an increase in CAMP in the incubation medium. The magnitude and significance of this extracellular cAMP accumulation were similar to those observed in the tissue and, accordingly, may form the basis of a simplified bioassay procedure for TSAb.