The inhibitory effect of noradrenaline on thyrotrophin-stimulated 3,5,3′-tri-iodothyronine and thyroxine release is mediated through a Ca2+-dependent process in the thyroid gland of the mouse

Abstract

ABSTRACT We examined the effect of noradrenaline on the release of 3,5,3′-tri-iodothyronine (T3) and thyroxine (T4) from perifused mouse thyroid. Noradrenaline suppressed the thyrotrophin (TSH)-stimulated release of T3 and T4. The addition of prazosin, which is a specific α1 antagonist, or the depletion of Ca2+ from the perifusion buffer completely abolished the inhibitory effect of noradrenaline on TSH-stimulated T3 and T4 release. Noradrenaline did not inhibit TSH-stimulated cyclic adenosine 3′,5′-monophosphate (cAMP) release in the presence of 3-isobutyl-1-methylxanthine (IBMX), which inhibits both cAMPspecific and calmodulin-sensitive phosphodiesterases. Noradrenaline significantly suppressed the TSH-stimulated release of T3 and T4 in the presence of IBMX. These results suggest that the inhibitory effect of noradrenaline on TSH-stimulated T3 and T4 release is not mediated through a cAMP-dependent process or the activation of a calmodulin-sensitive phosphodiesterase, and that this inhibition is mediated through a Ca2+-dependent process regulated by the α1-adrenergic system in the mouse thyroid. Journal of Endocrinology (1993) 138, 73–80