| Summary: | Thyroid hormones play crucial roles in regulation of growth, metabolism, reproduction, and other essential physiological processes. In mammals, thyroid hormone synthesis is dependent on uptake of iodine from the blood into thyroid tissue by the sodium-iodide symporter (NIS) protein, with diet being the ultimate iodide source. In contrast, it has been proposed that fish can obtain iodide directly from their environment by pumping it across gills. My study was designed to determine whether fish possess both gill and gut iodide uptake mechanism by characterizing NIS mRNA expression in gill and gut tissues of the red drum. PCR primers for NIS were designed using Clustal X primer design software. Tissue enriched in thyroid follicles located ventral to and between the 2nd and 4th gill arches was collected along with gill and gut for mRNA extraction. NIS was detectable in the thyroid tissue, gill, gut, and brain tissues. Expression in both gill and gut tissues suggests two possible mechanisms of iodide absorption in red drum. NIS expression in the brain is a novel discovery and warrants further studies as to its function and specific location.
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