久效磷对斑马鱼胚胎期心脏和骨骼发育的毒性效应研究

Study of the Toxicity of Monocrotophos on the Cardiac and Skeletal Development of Danio rerio Embryos

有机磷农药具有一定的胚胎发育毒性,以往有机磷农药胚胎发育毒性的研究主要集中于个体水平。本研究以斑马鱼(Danio rerio)作为受试生物,采用0.000 4、0.004、0.04和0.4mg/L的久效磷自受精卵暴露斑马鱼胚胎至受精后96h(96hpf)。研究结果表明,久效磷对胚胎的存活率、孵化率均无显著影响,但显著降低了36hpf胚胎的心率,96hpf仔鱼心包囊肿率和脊柱弯曲率显著升高;久效磷暴露胚胎至48hpf显著降低了心脏发育相关基因(Tbx2)的表达水平、显著升高了肌肉发育相关基因(Mef2c)的表达水平。可见,久效磷能够在个体和分子水平上影响斑马鱼胚胎心脏和骨骼的发育,对斑马鱼胚胎心脏和骨骼的发育具有毒性效应。

Monocrotophos （MCP, CAS number 6923-22-4）, an organophosphate pesticide, can adversely affect the normal development of mammal embryos, however, its toxicity on the heart and skeleton devel- opments of fish embryos has not been reported. Moreover, previous researches on the embryo toxicity of organophosphorus pesticides were mainly performed at the individual level, with few studies combining with molecular indicators to further explore the underlying mechanisms. Therefore, using zebrafish as the model animal, the toxicity of MCP on the heart and skeleton development was investigated at both the in- dividual and molecular levels in this study. Embryos were exposed to 0. 000 4, 0. 004, 0.04 and 0. 4 mg/L monocrotophos from 0 h post fertilization （hpf） to 96 hpf. The results showed that compared with the control group, there were no significant changes for the survival and hatching rates of embryos in all treat- ment groups. However, pericardial cyst was observed in larvae exposed to MCP at 96 hpf, with the fre- quencies of this deformity significantly increased in all treatment groups. Meanwhile, the heartbeat fie- quencies decreased significantly at 36 hpf in the 0. 000 4, 0.04 and 0.4 mg/L treatment groups. Our data indicate damages on the structure and function of the zebrafish hearts caused by MCP exposure. It is re- ported that abnormal morphologies such as pericardial cyst and ventricular dysplasia would be induced when Tbx2 gene expression is suppressed in zebrafish embryos. Considering the mRNA expressions of Tbx2 decreased significantly in the 0.04 and 0.4 mg/L treatment groups at 48 hpf, we deduced that high concentrations of MCP may affect the heart development through inhibiting the gene expression of Tba2, at least partly. The fact that mRNA expressions of Tbx2 were not changed by MCP at 60 hpf may be ex- plained by the completion of heart development at this time point. In addition, the skeleton development of embryos was also affected by MCP, with the percentages of spinal curvature increased significantly by 0. 004-0.4 mg/L MCP at 96 hpf. Muscle development related gene Mef2c is one of the key genes respon- sible for the normal development of skeletal muscles, which plays an important role in bone growth. Our results found that the mRNA expressions of Mef2c increased significantly in the 0.4 mg/L treatment groups at 48 hpf, thus it could be speculated that MCP may impact the development of skeletal muscle by disturbing the normal expression pattern of MIef2c. However, other genes like MyoD and Myf5 should be further investigated in future studies, as mRNA expressions of Mef2c exhibited no significant changes in other treatment groups. In conclusion, this study provided basic information on the toxicity of MCP on the heart and skeleton development of fish embryos at both the individual and molecular levels.