title: MCT8 is Downregulated by Short Time Iodine Overload in the Thyroid Gland of Rats.
abstract: Wolff-Chaikoff effect is characterized by the blockade of thyroid hormone synthesis and secretion due to iodine overload. However, the regulation of monocarboxylate transporter 8 during Wolff-Chaikoff effect and its possible role in the rapid reduction of T4 secretion by the thyroid gland remains unclear. Patients with monocarboxylate transporter 8 gene loss-of-function mutations and monocarboxylate transporter 8 knockout mice were shown to have decreased serum T4 levels, indicating that monocarboxylate transporter 8 could be involved in the secretion of thyroid hormones from the thyroid gland. Herein, we aimed to evaluate the regulation of monocarboxylate transporter 8 during the Wolff-Chaikoff effect and the escape from iodine overload, besides the importance of iodine organification for this regulation. Monocarboxylate transporter 8 mRNA and protein levels significantly decreased after 1 day of NaI administration to rats, together with decreased serum T4; while no alteration was observed in LAT2 expression. Moreover, both monocarboxylate transporter 8 expression and serum T4 was restored after 6 days of NaI. The inhibition of thyroperoxidase activity by methimazole prevented the inhibitory effect of NaI on thyroid monocarboxylate transporter 8 expression, suggesting that an active thyroperoxidase is necessary for MCT8 downregulation by iodine overload, similarly to other thyroid markers, such as sodium iodide symporter. Therefore, we conclude that thyroid monocarboxylate transporter 8 expression is downregulated during iodine overload and that the normalization of its expression parallels the escape phenomenon. These data suggest a possible role for monocarboxylate transporter 8 in the changes of thyroid hormones secretion during the Wolff-Chaikoff effect and escape.
authors.affiliation: Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: E C L
authors.initials: ECL
authors.lastname: de Souza
authors.affiliation: Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: G R M
authors.initials: GRM
authors.lastname: Dias
authors.affiliation: Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: R C
authors.initials: RC
authors.lastname: Cardoso
authors.affiliation: Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.|Departamento de Ciências Básicas, Pólo de Nova Friburgo, UFF, Brazil.
authors.forename: L P
authors.initials: LP
authors.lastname: Lima
authors.affiliation: Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: R S
authors.initials: RS
authors.lastname: Fortunato
authors.affiliation: Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: T J
authors.initials: TJ
authors.lastname: Visser
authors.affiliation: Universitary Hospital Clementino Fraga Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Vaisman
authors.affiliation: Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.|Polo de Xerém/NUMPEX, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: A C F
authors.initials: ACF
authors.lastname: Ferreira
authors.affiliation: Laboratory of Endocrine Physiology Doris Rosenthal, Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: D P
authors.initials: DP
authors.lastname: Carvalho
mesh_terms: D027182:Amino Acid Transport System y+ / Q000032:analysis; D000818:Animals; D015536:Down-Regulation; D027301:Fusion Regulatory Protein 1, Light Chains / Q000032:analysis; D007455:Iodine / Q000378:metabolism*; D008297:Male; D027501:Monocarboxylic Acid Transporters / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013961:Thyroid Gland / Q000378:metabolism*; D013963:Thyroid Hormones / Q000378:metabolism
chemical_list: D027182:Amino Acid Transport System y+; D027301:Fusion Regulatory Protein 1, Light Chains; D027501:Monocarboxylic Acid Transporters; C486582:Slc7a8 protein, rat; D013963:Thyroid Hormones; C478998:monocarboxylate transporter 8, rat; D007455:Iodine