Effects of Prolonged Exposure to Perchlorate on Thyroid and Reproductive Function in Zebrafish

Abstract

The objectives of this study were to determine the effects of prolonged exposure to perchlorate on (1) thyroid status and reproductive performance of adult zebrafish (Danio rerio) and (2) F1 embryo survival and early larval development. Using a static-renewal procedure, mixed sex populations of adult zebrafish were exposed to 0, 10, and 100 mg/l nominal concentrations of waterborne perchlorate for 10 weeks. Thyroid histology was qualitatively assessed, and females and males were separated and further exposed to their respective treatments for six additional weeks. Eight females in each tank replicate (n = 3) were paired weekly with four males from the same respective treatment, and packed-egg (spawn) volume (PEV) was measured each of the last five weeks. At least once during weeks 14-16 of exposure, other end points measured included fertilization rate, fertilized egg diameter, hatching rate, standard length, and craniofacial development of 4-day-postfertilization larvae and thyroid hormone content of 3.5-h embryos and of exposed mothers. At 10 weeks of exposure, perchlorate at both concentrations caused thyroidal hypertrophy and colloid depletion. A marked reduction in PEV was observed toward the end of the 6-week spawning period, but fertilization and embryo hatching rates were unaffected. Fertilized egg diameter and larval length were increased by parental exposure to perchlorate. Larval head depth was unaffected but the forward protrusion of the lower jaw-associated cartilage complexes, Meckel's and ceratohyal, was decreased. Exposure to both concentrations of perchlorate inhibited whole-body thyroxine content in mothers and embryos, but triiodothyronine content was unchanged. In conclusion, prolonged exposure of adult zebrafish to perchlorate not only disrupts their thyroid endocrine system but also impairs reproduction and influences early F1 development.

Physiological effects of polybrominated diphenyl ether (PBDE-47) on pregnant gartersnakes and resulting offspring

“…Previous work in frogs and birds has shown that females do transfer BDE-47 to their eggs (Liu et al, 2011;Verreault et al, 2006), and thus the offspring in this study were likely exposed. Our major finding was that the average mass of neonates tended to be larger in the BDE-47 treated animals, which is similar to findings in zebrafish exposed to the thyroid disruptor perchlorate during development (Mukhi and Patiño, 2007). Yet a study also conducted in zebrafish exposure during development to BDE-47 found that high concentrations yielded smaller individuals (Lema et al, 2008).…”

Thyroid endocrine system disruption by pentachlorophenol: An in vitro and in vivo assay

“…PCP decreased the plasma T4 levels in rats (BruckerDavis, 1998;Kawaguchi et al, 2008). Decreased T4 levels are frequently observed in mammals, amphibian and fish models exposed to TH endocrine disruptors, e.g., PBDEs (Tomy et al, 2004;Ellis-Hutchings et al, 2006;Lema et al, 2008;Yu et al, 2010), PCBs (Donahue et al, 2004;Martin and Klaassen, 2010;Schnitzler et al, 2011), and perchlorates (Mukhi and Patino, 2007;Opitz et al, 2009;Schmidt et al, 2012). Decreased TT4 and increased TT3 levels and the consequent increased ratio of T3/T4 are frequently observed in fish exposed to TH endocrine disruptors (Chen et al, 2012;Wang et al, 2013).…”

Changes of thyroid hormone levels and related gene expression in Chinese rare minnow (Gobiocypris rarus) during 3-amino-1,2,4-triazole exposure and recovery

“…Previous studies indicate that if such processes are disturbed by endocrine disrupting compounds, this could have a dramatic impact on the thyroid endocrine system and reproduction (Mukhi and Patino, 2007). The development of bioassays that measure changes in gene expression provide molecular strategies and increase mechanistic understanding of thyroid disruptive effects on development and homeostasis (Zhang et al, 2006;Veldhoen et al, 2006).…”