Octylphenol influence growth and development of Rana chensinensis tadpoles via disrupting thyroid function

Octylphenol (OP), a class of endocrine disrupting chemicals (EDCs), could produce adverse effects on developmental process of animals. Thyroid hormone is one of the important hormones involved in animal development. To determine whether OP affect the growth and development of amphibian larvae via interfering the thyroid function, Rana chensinensis larvae at Gosner stage 29 were exposed to 10^-8, 10^-7 and 10^-6 mol/L OP in the present study. Results demonstrated that OP could decrease the body length and mass and retard the development of tadpoles. The histologic evaluation showed microscopic structures of thyroid gland were changed in 10^-7 and 10^-6 mol/L OP treated groups on day 40. The expression levels of Dio2, Dio3, TRα and TRβ mRNA in the liver, brain, skin and tail of tadpoles were detected by qRT-PCR, when treated with OP for 20, 30, 40 and 50 day, respectively. The results of qRT-PCR showed OP could affect the expressions of Dio2, Dio3, TRα and TRβ mRNA in the four tissues, and then influence the activity and function of THs, further affecting the growth and development of the tadpoles.

Differentiations of 5-HT and GAS cells in the digestive canals of Rana chensinensis tadpoles

In the current study, 5-nydroxytryptamine (5-HT) and gastrin (GAS) cells in the digestive canals of Rana chensinensis tadpoles at different developmental stages were investigated by immunohistochemistry. Results showed that the 5-HT cells were only detected in the duodenum before metamorphosis began, and were extensively distributed in the stomach, duodenum, small intestine, and rectum thereafter, with the highest counts found in the duodenum and rectum when metamorphosis was completed. The GAS cells were only distributed in the stomach and duodenum, and only rarely detected in the duodenum before metamorphosis began, but increased in the stomach during metamorphosis and showed zonal distribution in the gastric mucosa when metamorphosis was completed. Metamorphosis is a critical period for amphibians, during which structural and functional physiological adaptations are required to transition from aquatic to terrestrial environments. During metamorphosis, the differentiations of 5-HT cells in the gastrointestinal canals of tadpoles could facilitate mucus secretion regulation, improve digestive canal lubrication, and help water-shortage food digestion in terrestrial environments. Conversely, GAS cell differentiations during metamorphosis might contribute to the digestive and absorptive function transition from herbivore to omnivore.