Iodine Balance in Rainbow Trout (Salmo gairdneri) and Effects of Testosterone Propionate

Abstract

Iodine balance was studied in immature rainbow trout (Salmo gairdneri) held at 12 °C in water of iodine content 1.85 μg/L and fed daily 1% of body weight with food containing 0.48 μg I/g. Iodide flux into the plasma pool was 148 ng I∙h−1∙100 g−1 of which < 1% was contributed by peripheral deiodination of thyroid hormones, up to 16% was obtained from the diet, and at least 84% was derived from the water. Less than 5% of iodide intake was required to satisfy thyroidal secretory demands. Testosterone injections elevated plasma iodide and protein levels, but did not alter the rate of plasma iodide turnover. Key words: trout, iodine balance, thyroid function, testosterone