Cadmium And Benzo [a] Pyrene On The Yangtze River Estuary Mudskipper Fish (periophthalmus Modestus) Toxic Effects,

1. The accumulation of heavy metal in different tissues of Periophthalmus modestusThe contents of Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺ ions in the different tissues of Periophthalmus modestus in Changjiang River were examined by trace element detecting method, the distributive and accumulative rules of these elements were studied. The result showed that the contents of four metal ions were significant different in the same tissues. No matter in the gill, liver or flesh the content of Zn²⁺ ions was most while Cd²⁺ ions was least. The accumulation sequence of four heavy metals in the same tissue was Zn²⁺> Cu²⁺> Pb²⁺> Cd²⁺.It also indicated that three kinds of tissues had different accumulation ability. The accumulation capability of these elements was ranked in the following order; gill>liver>flesh for copper, zinc and lead; while liver>gill>flesh for cadmium.2. Effects of Cd²⁺ and Benzo[a]pyrene on the antioxidant enzymatic system of Periophthalmus modestusLaboratory experiment was conducted to study the effects of Cd²⁺ on the activities of three kinds of antioxidant enzyme, superoxide dismutase (SOD), catalase (CAT), glutathione-peroxide (GSH-PX) in the liver of Periophthalmus modestus. The results indicated that in the group treated with 0.05 mg·L^-1 Cd²⁺, the activity of SOD increased with the prolonged exposure. In high Cd²⁺ level (0.5 mg·L^-1), the enzymatic activity was induced in the beginning of exposure time but decreased when time went on. It was significant lower than the control group after 7 days. It was also found that the change of the activities of CAT and GSH-PX in liver were similar to SOD. Initially, the activities of these enzymes in the each treated group were significant higher than the control group because of the induced effect. But this tendency was altered when time flies on. The activities of enzymes kept to fall after a while and finally came to the level lower than the control one.With the similar method, the activities of above-mentioned enzymes were analyzed after the fish expose to benzo[a]pyrene. The results were as follows. The activity of SOD was induced after one day and the higher the BaP concentration the more remarkable the effect. However, the activity of SOD reduced gradually to the normal level with the prolonged exposure. It was below to the level of control group at end of the exposure. On the other hand, the activities of CAT and GSH-PX in high BaP concentration treated group decreased with time going on. But in the low BaP level, the activities had a multiple variation. Furthermore, there was no marked relation of time and dose-respond.3. Effects of Cd²⁺ and Benzo[a]pyrene on EROD activities in liver of Periophthalmus modestusChanges of EROD activities in liver of Periophthalmus modestus with Cd²⁺ and benzo[a]pyrene exposure were respectively studied in experimental condition. The results were as follows: Cd²⁺ exposure can induce the EROD activities in liver, but there was no distinct dose-respond relationship. With the prolonged exposure, EROD activities in different treated group had variance changing tendency. Some were maximum at certain times, while others increase all the time. BaP can also increase the EROD activities in liver with the prolonged exposure. However, the activity of EROD in high BaP level (0.5 mg· L^-1 Bap) decreased after 10d exposure. It had a marked peak at 7^th day.4. Effects of Cd²⁺ and Benzo[a]pyrene on the ultrastructure of hepatic cells of Periophthalmus modestusBy using transmission electron microscopy (TEM), the effect of Cd²⁺ and benzo[a]pyrene at two separate concentrations on the ultrastructures of hepatic cells of Periophthalmus modestus were investigated. The results showed that the organelles in hepatic cells of Periophthalmus modestus were damaged to different extents after the fish was exposed under lower Cd²⁺ concentration(0.1 mg · L^-1) for 10 days. Ultrastructural alterations included mitochondrial condensation, swelling, and lysis. The endoplasmic reticulum showed slight dilation, fragmentation and vesiculation. Other organelles, such as nucleolus, had different extents injury including nuclear degeneration, condensation. After exposure there were also numerous large lipid droplets and abundant stored glycogen. While the fish exposed under the higher Cd²⁺ concentration (1mg· L^-1) for 10 days, almost all of organelles in the hepatic cells were affected by cadmium exposure. The severity extents of such changes were dependent on the concentration level of Cd²⁺.The organelles of in hepatic cells Periophthalmus modestus which exposed to BaP were also damaged to different extents. Mitochondria and endoplasmic reticulum were the chief organelles affect by cadmium exposure. The ultrastructure showed damage of nuclear, absence of organelles, massive swollen mitochondria with loss of cristae, markedly swollen endoplasmic reticulum. In short, the results were the same as cadmium exposure. It can be conclude that Cd²⁺ and benzo[a]pyrene had similar mechanism of the toxic effects on the ultrastructures of hepatic cells of Periophthalmus modestus...