Effect of Iodoarachidonates on Thyroid FRTL-5 Cells Growth

Summary Excess iodide inhibits several thyroid parameters, by a putative organic iodocompound. Different iodolipids, including iodinated derivatives of arachidonic acid (IAs), are produced by rat, calf and pig thyroid. The action of two iodolactones, one bearing the iodine atom at the position 6 (IL-d) and the other at position 14 (IL-w) on growth of FRTL-5 cells was studied. KI, IL-w and IL-d exert a dose-related inhibition on FRTL-5 cell profileration. The first two compounds caused inhibition at 1 μM while IL-d was effective at 10 μM. This inhibitory action of iodolactones (ILs) was not altered by 1 mM methyl-mercaptoimidazol (MMI), indicating that they exert their effect per se. The action of ILw on cell growth was reversible. The growth-stimulating effect of 10 uM forskolin was inhibited by IAs, showing that one possible site of action lies at the cAMP pathway. The present results give further support to our hypothesis about the role of IAs in thyroid growth autoregulation.