Extrathyroidal Effects of Low Concentrations of Thiourea on Rainbow Trout, Salmo gairdneri

Abstract

Chronic exposure of fed immature rainbow trout (Salmo gairdneri) to a low ambient thiourea (TU) concentration did not depress circulating levels of T4 (thyroxine) or triiodothyronine, T4 degradation rate, or T4 deiodination rate indicating no significant T4 influence on thyroidal hormone output. However, TU increased the hematocrit and decreased distribution spaces for iodide and T4, indicating direct sensitivity of extrathyroidal processes to TU.Key words: thiourea, thyroxine, hematocrit, iodide metabolism, rainbow trout