Toxicity Of Tributyltin (Bis[tri-n-butyltin] Oxide, TBTO) On Asian Clam Ruditapes Philippinarum

Endocrine disrupting chemicals (EDCs), also called Endocrine disrupters or Environmental hormones, are chemicals that are capable of affecting endocrine system and, act as natural incretions or hormonal resistant, resulting in disruption of the production, release, metabolism, combination, excretion and function of hormone. Since 1996, effects of EDCs on humans and wildlife have come to public attention.We choose clam Ruditapes philippinarum as experimental animal and Tributyltin (Bis[tri-n-biityltin]oxide, TBTO, C24Hs4OSn2) as the endocrine disrupter for its high inducing capability and still existing in the environment. In the experiment, BCFs (bioconcentration factor) and the manner of concentration were studied. With changes of microstructure/ultrastruture in digestive diverticula, gill, mantel and histochemistry of digestive diverticula, a systematic work has been done on the toxicity and endocrine disrupting effects of TBTO on Ruditapes philippinarum.To understand the BCFs and concentration manner of TBTO by Ruditapes philippinarum, a constant concentration of TBTO 200ng/L was set with different exposure time. The experiment took 5 weeks. Gas Chromatography-Electron Capture Detection was used as detection and quantification method for TBTO in clam's tissues (low detection limit: 20ng/ml, regression line: Y=0.7062X+12.949 and linearity range: lOOng/g-lOOOng/g as TBTO). The results, after one week, showed that each tissue's BCFs are all over 300, and they rose up with the extension of exposure time. The maximum BCF digestive diverticula reached at the end of the experiment is more than 3000. Most groups' results are different (p<0.05) except digestive diverticula's IV and V (p=0.08).Damages of TBTO on the structure of Ruditapes Philippinarum increased with exposure time: (l)digestive diverticula: one week: lightly dilation of basophil and digestive cell nuclear membrane, endoplasmic reticulum dilation; two weeks, partial fused crista mitochondria, slightly twisted chorion, part of cell base vacancy, reticulumappearing between cell and hepatocyte, forming of gaps between cells; after two weeks, most endoplasmic reticulum dilation and vacuolation were founded. In hepatocyte, the most sensitive organelle to TBTO of clam under long-term exposure is endoplasmic reticulum, and sub-sensitive one is mitochondria.(2)During the first two weeks, with treatment of TBTO (200ng/L), part of nuclear membranes of gill epithelia slightly dissolved, cell endoplasmic reticulum partly dilated and several chromatins has been agglomerated; further, most cytoplast dissolved after two weeks and, incomplete nuclear membrane, chorion slightly dilation, appearing of endoplasmic reticulum vacuolation and some mitochondria dissolved. (3) There are similar effects of TBTO on the mantle and gill of the subject.The activity of digestive diverticula's acid phosphatase, alkaline phosphatase and cytochrome oxidase decreased with the prolonging of exposure to TBTO, and can be judged from the fade of tissues, but there are little changes on principal active positions. No topical abnormity was observed.