In this study, we have identified several ovarian steroids in Ciona with high similarity to vertebrate steroids andshowed that cholesterol, corticosterone, dehydroepiandrosterone, estrone, estradiol-17β, testosterone,pregnenolone, progesterone, have identical molecular spectra with vertebrate steroids. In addition, we havestudied the effects of an endocrine disruptor (tributyltin: TBT) on these sex hormones and their precursors,ovarian morphology, and gene expression of some key enzymes in steroidogenic pathway in the ovary of Ciona.Ovarian specimens were cultured in vitro using different concentrations of TBT (10−5, 10−4 and 10−3 M).Ethanol was used as solvent control. Gene expression analysis was performed for adrenodoxin (ADREN) andadrenodoxin reductase (ADOX) (mediators of acute steroidogenesis) and 17β-hydroxysteroid dehydrogenase(17β-HSD). These transcripts were detected and measured by quantitative (real-time) polymerase chainreaction (qPCR). Sex steroids and their precursors were identified and quantified by a gas chromatographymassspectroscopy (GC-MS) method. Exposure of Ciona ovaries to TBT produced modulations (either increasedor decreased) of sterols and sex steroid levels, whereas no significant differences in ADREN, ADOX or 17β-HSDmRNA expression patterns were observed. Histological analysis shows that TBT produced severalmodifications on Ciona ovarian morphology that includes irregular outline of nuclear membrane, lesscompacted cytoplasm, in addition to test and granulosa cells that were detached from the oocyte membrane.Given that the ascidians represent very simple experimental models for the study of endocrine disruption byenvironmental contaminants, our findings provide excellent models for multiple identification andquantification of sex steroid and their precursors in biological samples exposed to endocrine-disruptingchemicals and for direct extrapolation of such effects across taxonomic groups and phyla. In addition, theseresults suggest that Ciona intestinalis may be a suitable species for molecular ecotoxicological studies andbiomarker model for endocrine-disrupting effects in marine invertebrates.
|Numero di pagine||10|
|Rivista||Toxicology and Applied Pharmacology|
|Stato di pubblicazione||Published - 2010|
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