Forskolin stimulation of thyroid secretion of T 4 and T 3

Abstract

Forskolin is a potent activator of adenylate cyclase in many tissues including the thyroid gland. We compared the effects of 10 −5 M forskolin and 100 μunits/ml TSH on the dynamics of T 4 and T 3 secretion from perfused dog thyroid lobes. Both agents induced pronounced increases in T 4 and T 3 secretion. The increase in secretion was significantly steeper during forskolin than during TSH stimulation. This may suggest that early processes such as TSH—receptor interaction and the subsequent activation of the catalytic unit of adenylate cyclase are of importance for the pattern of very gradual increase in hormone secretion during TSH stimulation of the thyroid. In other respects forskolin seems to induce absolute and relative secretion of T 3 and T 4 very similar to those obtained by cAMP and TSH.