Localization and Enzyme Activity of Iodotyrosine Dehalogenase 1 during Metamorphosis of Frog Microhyla ornata

Abstract

The distribution and activity of iodotyrosine dehalogenase 1 (DEHAL1) enzyme was determined during metamorphosis of the frog Microhyla ornata. Immunohistochemical and enzymatic studies in the thyroid, olfactory system, brain, skin, and tail of frog were performed. DEHAL1-positive cells were seen in the olfactory epithelium, the nucleus infundibularis ventralis, the ventricular lining, cerebellum in the brain, in the pituitary gland, in the mucus glands of skin, and in epithelial cells of tadpole tail fin. During metamorphosis, DEHAL1 enzyme activity was also detected in the above-mentioned frog tissues with the enzyme exhibiting higher activity on diiodotyrosine (DIT) as compared to monoiodotyrosine (MIT). Using DIT as a substrate, maximal activity was detected at stage 44 in the brain (157.7 U/mg protein), while it was higher at stage 42 in the tail (138.5 U/mg protein). With MIT as a substrate, highest activity was detected in the brain at stage 42 (65.8 U/mg protein). Thus, the localization, relative levels, and specificity of DEHAL1 suggest that it might be involved in tissue-specific deiodination of MIT and DIT, thus making free iodine available, and therefore plays an essential role during metamorphosis in M. ornata.

Analysis of candidate genes for morphine preference quantitative trait locus Mop2

“…The role of Iyd in the thyroid gland is to scavenge iodine from diiodotyrosine (DIT) and monoiodotyrosine (MIT); byproducts of the formation of thyroid hormone from thyroglobulin. Nonetheless, Iyd is expressed in the frontal cortex, the thalamus and the hippocampus of mouse brain (Allen Brain Atlas; Newrzella et al, 2007) as well as in brain regions of other species (Gaupale et al, 2009) where its role remains unknown. Despite the efficient nature of lysosomal uptake and recycling of MIT and DIT in the thyroid gland (Gnidehou et al, 2004; Rokita et al, 2010), it is controversial whether these halogenated tyrosine byproducts ever gain access to the general circulation from the thyroid gland, and gain access to the brain by crossing the blood-brain barrier (Weinert et al, 1967; Wellby and O'Halloran, 1969).…”

Evaluating Iodide Recycling Inhibition as a Novel Molecular Initiating Event for Thyroid Axis Disruption in Amphibians

“…The IYD amino acid sequence is highly conserved and homologous proteins have been identified from a wide range of organisms (Phatarphekar et al, 2014). In amphibians, IYD has been documented in three frog species (Xenopus laevis, Xenopus tropicalis, and Microhyla ornata) (Fujimoto et al, 2012;Gaupale et al, 2009). IYD inhibition has been partially evaluated in the mammalian system with several in vivo and in vitro studies.…”