INHIBITION BY IODIDE OF THE CHOLINERGIC STIMULATION OF PROSTAGLANDIN SYNTHESIS IN DOG THYROID

Iodide is shown to inhibit the cholinergic stimulation of prostaglandin E2 (PGE2) and F2a(PGF2a) synthesis in dog thyroid slices. The inhibitory effect of iodide was already detectable at 1 μM and reached its maximal level at 10 μM. At this concentration, iodide inhibited the carbamylcholine-stimulated release of PGE2 and PGF2a by 59% and 73%, respectively (eight experiments). The effect of iodide was neither immediate nor rapidly reversed after a change of incubation medium. The unstimulated release of PGE2 and PGF2a and the stimulation by epinephrine and ionophore A23187 were not modified by iodide in concentrations up to 0.1 mM. The effect of iodide was suppressed in the presence of methimazole (0.1 mM) but not NaC104 (2 mM). Iodide (0.1 mM) did not inhibit the stimulation by carbamylcholine of PGF2a and PGE2 release by rat pancreas in vitro. These data demonstrate a new action of iodide on the thyroid and establish a link among iodide metabolism, PG synthesis, and cholinergic action in the dog thyroid. © 1979 by The Endocrine Society.