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

Abstract

a b s t r a c tThyroid hormones (THs) play an important role in the development and metabolism of fish through their influences on genetic transcription and are targets for endocrine disruptive agents in the aquatic environment. Amitrole is a pesticide potentially interfering with thyroid hormone regulation. In this study, the rare minnow (Gobiocypris rarus) was exposed to different levels of 3-amino-1,2,4-triazole (amitrole) and allowed to recover in clean water. Plasma TH levels and the expression of TH-related genes, including transthyretin (ttr), deiodinases (d1 and d2), and the thyroid hormone receptor (tr˛) from the livers and brains were evaluated. After exposure, the plasma TH levels did not change. Histopathological observations showed that livers were degenerated at 10,000 ng/l and these damages could be recovered by the withdrawal of amitrole. However, the ttr, d1, and d2 mRNA levels in the livers of males were significantly up-regulated in all exposure groups (p < 0.05). The ttr and d2 mRNA levels were significantly up-regulated at 10,000 ng/l and 10, 100, and 1000 ng/l in the livers of females, respectively (p < 0.05). In the brains of males, a twofold increase of d2 mRNA levels at ≥100 ng/l and a fivefold decrease of tr˛mRNA levels at ≥10 ng/l were observed (p < 0.05), whereas no significant differences were observed in the expression of d2 and tr˛in the brains of females. After a recovery period, the ttr, d1, and d2 mRNA levels in the livers of males returned to control levels, but the tr˛mRNA levels were irreversibly decreased at all treatments (p < 0.05). In addition, the d2 mRNA levels in the livers of females were significantly induced at ≥100 ng/l. Moreover, the d2 mRNA levels in the brains of males and females were up-regulated at 10,000 ng/l. These results indicated that amitrole exposure could result in alternations of ttr, d1, d2, and tr˛gene expression in different tissues of the rare minnow. The expression of these TH-related genes in males was more sensitive to amitrole than those of females. Recovery in clean water was associated with the selective regulation of TH-related gene transcription in the rare minnow. Therefore, these TH-related genes can serve as biomarkers to screen the effects of thyroid disruption chemicals in rare minnow.

The Levels of Serum Thyroid Hormone in Sturgeon Populations

“…Although the T3 half-life is only 1 day, its activity is stronger than T 4 .The contents of T 3 and FT 3 , T 4 and FT 4 showed extremely significant positive correlation in this study. The result is similar to that reported by Eales and Shostak about rainbow trout [12]. It is indicated that there is a coordination mechanism in serum T 3 and FT 3 or T 4 and FT 4 , which have mutual feedback on hypothalamic pituitary thyroid axis.…”

Transcriptional expression analysis of ABC efflux transporters and xenobiotic-metabolizing enzymes in the Chinese rare minnow

“…The brood stock of rare minnow was raised in a flow through system with dechlorinated tap water (pH: 7.2-7.6; hardness: 44-61 mg CaCO 3 l −1 ; and temperature: 25 ± 1 • C) with a photo period of 16:8 h (light:dark) and has been used for testing chemicals in our laboratory for more than 10 years (Zha et al, 2007;Li et al, 2009). The fish were fed on commercial food pellet (Trea, Germany) at a rate of 0.1% body weight per day and newly hatched brine shrimp (Artemia nauplii) two times daily.…”

“…The quantity and quality of the RNA were determined by a spectrophotometer (Thermo Fisher, San Jose, CA, USA), the ratio of OD260/280 was range from 1.8 to 2. The protocol of RT-PCR is according to previous report of our laboratory (Li et al, 2009).…”

“…After 12 days exposure, the body lengths and body weights of the rare minnows were measured. Then the fish were sacrificed, the tissues in each group were fixed in Bouin's solution for histopathological examination, the detailed protocol of histopathology was according to previous description of our laboratory (Zha et al, 2007;Li et al, 2009), and tissues from the rest of rare minnow were flash-frozen in liquid nitrogen, and stored at −80 • C.…”

“…The rare minnow is distributed mostly in the upstream region of the Yangtze River and in the Sichuan Province of China. It is considered to be an appropriate species for the assessment of chemical toxicity due to its small size, ease of culture, short life cycle and prolific egg production with high fertilization and hatching rates (Zha et al, 2007;Li et al, 2009).…”