| dc.description.abstract | The thyroid gland is known to be important in the regulation of metabolism,growth, and reproduction in both mammalian and non-mammalian species. However, little information is available how thyroid hormones act on target tissues in non-mammalian species such as fish. Fish are difficult to study because we do not currently have an effective, non-invasive method for administering thyroid hormone to them or for studying the effects of altered thyroid hormone levels on their tissues. As a result, research done on fish often utilizes pharmacological dosages of stressfully-administered thyroid hormone, causing experimental artifacts. In my study, I developed a thyroid hormone immersion system to
generate physiological increases of the thyroid hormone thyroxine (T4) in the red drum (Sciaenops ocellatus), a commercially important fish species. Immersion experiments were performed, where red drum were kept in 20-gallon glass tanks – with either T4-treated or control solution-treated tank water, and the system recirculating water flow turned off – for the course of the set immersion period. Immersion in T4-treated tank water for 40 hours induced an increase in circulating T4 from 8.3 ng/mL (in control fish) to 28.7 ng/mL (in T4-treated fish), within the physiological range. This physiological elevation of T4 did not induce significant changes in liver IRD gene expression, considered to be a marker of
pharmacological elevation of thyroid hormones. These results showed that thyroid hormone immersion should be an effective, non-invasive method for administration
of physiological levels of thyroid hormone to red drum. | en |
