Altered Expression of Thyroid- and Calcium Ion Channels-Related Genes in Rat Testes by Short-Term Exposure to Commercial Herbicides Paraquat or 2,4-D

Exposure to pesticides such as paraquat and 2,4-dichlorophenoxyacetic acid (2,4-D) has been linked to harmful health effects, including alterations in male reproduction. Both herbicides are widely used in developing countries and have been associated with reproductive alterations, such as disruption of spermatogenesis and steroidogenesis. The thyroid axis and Ca²⁺-permeable ion channels play a key role in these processes, and their disruption can lead to reproductive issues and even infertility. This study evaluated the short-term effects of exposure to commercial herbicides based on paraquat and 2,4-D on gene expression in rat testes. At the molecular level, exposure to paraquat increased the expression of the thyroid hormone transporters monocarboxylate transporter 8 (<i>Mct8</i>) and organic anion-transporting polypeptide 1C1 (<i>Oatp1c1</i>) and the thyroid receptor alpha (<i>TRα</i>), suggesting a possible endocrine disruption. However, it did not alter the expression of the sperm-associated cation channels (<i>CatSper1-2</i>) or vanilloid receptor-related osmotically activated channel (<i>Trpv4</i>) related to sperm motility. In contrast, exposure to 2,4-D reduced the expression of the <i>Mct10</i> transporter, <i>Dio2</i> deiodinase, and <i>CatSper1</i>, which could affect both the availability of T3 in testicular cells and sperm quality, consistent with previous studies. However, 2,4-D did not affect the expression of <i>CatSper2</i> or <i>Trpv4</i>. Deregulation of gene expression could explain the alterations in male reproductive processes reported by exposure to paraquat and 2,4-D. These thyroid hormone-related genes can serve as molecular biomarkers to assess endocrine disruption due to exposure to these herbicides, aiding in evaluating the health risks of pesticides.