Influence of potassium thiocyanate on thyroid function of rainbow trout, Salmo gairdneri.
Sublethal doses of potassium thiocyanate (KSCN), an iodide competitor, depressed thyroidal radioiodide uptake of fed laboratory rainbow trout at 11 degrees, but did not depress either plasma levels of T4 (L-thyroxine) and T3 (triiodo-L-thyronine) or radioiodide incorporation into plasma iodothyronines. Furthermore, plasma T4 levels of KSCN-treated trout increased to levels comparable to those of control trout in response to bovine TSH. The apparent inability of KSCN to inhibit thyroid hormone synthesis and release may be due to non-carrier-mediated iodide diffusion into the thyroid from the high iodide concentration normally found in plasma of freshwater salmonids. In conclusion, KSCN is not a practical inhibitor of thyroid hormone release in laboratory trout, and thyroid radioiodide uptake is a highly misleading index of thyroidal status.
D000818:Animals; D007454:Iodides / Q000097:blood; D013861:Thiocyanates / Q000494:pharmacology*; D013961:Thyroid Gland / Q000187:drug effects*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014337:Trout
D007454:Iodides; D013861:Thiocyanates; D014284:Triiodothyronine; D013974:Thyroxine; C009941:potassium thiocyanate