Mechanisms For Endocrine Disrupting Effects Of Environmental Estrogens:17β-E₂in Chlamys Farreri

Endocrine disrupting chemicals (EDCs) are chemicals that at certain doses, can interferewith the endocrine (or hormone system) in organisms. These disruptions can cause canceroustumors, birth defects, and other developmental disorders. Any system in the body controlled byhormones, can be derailed by hormone disruptors. Most research on adverse effects of EDCs hasfocused on impacts to the vertebrates in past years. However, much less is known about theeffects of endocrine disruption in the invertebrate phyla which represent~95%of all animalspecies, despite the fact that alternation in the sexual development of certain mollusks species bythe organotin compounds. Recently, an increasing amount of evidence that is the incidences ofintersex (feminization) in many bivalve species had been found in coastal worldwide, implyingthat EDCs did the adverse impacts on the bivalves in reproduction, population and ecologicalfunctions. And so, it is one of key issues to understand the potential mechanism of intersex inbivalves, which is helpful to reduce the ecological risk caused by EDCs and to strengthenvironmental management.Zhikong Scallop Chlamys Farreri is a native bivalves and one of the most importantaquaculture species in China coast. The present study analyzed their endogenous hormonevariations in Zhikong scallop Chlamys Farreri during a reproductive cycle using UPLC-MS/MS.Synchronized with the gonad development, the T levels exhibited a similar temporal patterncharacterized by one peak in spawning stage. While, E2concentrations increased at thedevelopment stage and then decreased sharply before maturation stage, which didn’t show asimilar trend with the gonad development. However, E1concentrations were lower than E2and Tsignificantly, and it didn’t vary obviously during the sampling period. In females, E2concentrations, were higher significantly than that in males, especially in the spawning stage.Similar to T in males, E2levels showed a significant peak in the maturation stage, and thendecreased sharply after spawning, which was agreed with the gonad development cycle. T levels,were similar to those of in males, but showed two peaks during the samplings. And E1concentrations were higher than those in males. All of these implied their functions asendogenous modulators regulate the gametogenesis. Then, Vtg, ER, CaM-1, and CaM-2mRNAexpressions normalized to EF-l α were quantified in gonad of Zk-scallop at differentdevelopment stages in a reproduction cycle: the Vtg and CaMs mRNA expression went onincreasing stably. Contrast to the Vtg and CaMs expressions, ER expressions remained the verylow levels. Thus, we speculate that there might be another pathway as an alternative way to theER pathway. Using the high-throughput sequencing technology (454), the gonad transcriptome of scallopexposed to E2was developed,, and the total of51997unigenes with average length of626bpwere obtained. After statistical analysis,60unigene showed differential expression significantlybetween the treatment group and the control group, and32unigenes increased with theincreasing concentration of E2. Of course, a large group of genes related to molecular functions,cellar component and biological process such as growth, development, reproduction, and signaltransduction were also found in the present database. Thus, all of these provided amount ofbiological information on identifying the potential mechanisms of endocrine disrupting behaviorin bivalves.