Effects of waterborne cadmium on thyroid hormone levels and related gene expression in Chinese rare minnow larvae

Cadmium is a heavy metal abundant in the environment that can induce endocrine disorder and toxicity in aquatic organisms at low levels. However, its effects on the thyroid system in fish are still unclear. In this study, the thyroid hormone (TH) levels and the expression profiles of genes related to hypothalamic-pituitary-thyroid (HPT) axis, including corticotropin-releasing hormone (crh), thyroid stimulating hormone beta (tsh beta), solute carrier family 5 (sodium iodide symporter) member 5 (slc5a5), thyroglobulin (tg), thyroid hormone receptor alpha (tr alpha) and thyroid hormone receptor beta (tr beta), were determined in whole body of Chinese rare minnow (Gobiogpris rams) larvae after exposure to different levels of Cd2+ (0, 0.5 and 2.5 mg/L) for 4 days. And the 96-h lethal concentration of Cd2+ on rare minnow larvae was determined as 2.59 mg/L. The results showed that crh, slc5a5, tg and tsh beta mRNA levels were significantly up-regulated in the larvae, but the gene expression of tr alpha and tr beta was down-regulated in a concentration-dependent manner. Besides, the This levels decreased in the whole-body of fish, especially the thyroxine (T4) level. The above results indicated that Cd2+ could alter gene expression in the HPT axis that might subsequently contribute to thyroid disruption. (C) 2014 Elsevier Inc. All rights reserved.