Mechanism Of The Inhibitory Effects Of Phthalate Esters On Karenia Brevis

Platicizers were widely used and produced a lot. There are many kinds of platicizers, among them phthalate esters (PAEs) were most used. In China, PAEs, such as DBP and DEHP, were detected in lots of rivers, such as Hei Longjiang River, Huanghe River, Changjiang River and Zhujiang River. Ocean algae were primary productivity of ocean ecosystem, they are important for keeping the balance of ocean ecosystem. PAEs were proved as a kind of environmental hormones, it can harm human’s reproductive system, endocrine system, et al. If PAEs which in ocean can be toxicity to ocean algae, and destroy the balance of ocean ecosystem.In this study, Karenia brevis was used, and 11 kinds of PAEs, DMP, DEP, DAP, DBP, DIBP, BBP, DHP, DOP, DEHP, DINP, DIDP, were used to study the toxicity of PAEs to K. brevis. And the mechanism of PAEs inhibited growth of K. brevis was considered with relation with oxidative stress caused by PAEs. We reported the mechanism of PAEs inhibited growth of K. brevis, and provided support to evaluate if PAEs are a threat to ocean ecosystem.From the results, toxicity effects of different PAEs were different to K. brevis. For these PAEs whose alkyl chain length are less than 6, the value of EC50.96h, turned less as increased the length of alkyl chain. The growth of K. brevis was inhibited under exposure of DEP, DAP, DBP, DIBP, BBP, respectively and were not inhibited by other 6 PAEs. Under DEP, DAP, DBP, DIBP, BBP exposure, algal numer was obviously decreased as control, respectively. And algal number was less in high concentration groups, and the contrast was grater as time passed. Algal numer of other 6 PAEs groups was not different as control. Under exposure of respective DBP, DIBP, BBP, contents of chl-a was obviously decreased. Other 6 PAEs didn’t effect the content of chl-a. Under exposure of respective DEP, DAP, DBP, BBP, MDA content was obviously increased as control. And MDA content was more in high concentration groups and increased as time passed. After 96h exposure, MDA content was up to the maximum value or was changed gently. Activities of SOD and CAT were both at first increased and then decreased. It proved that, the activity of antioxidant enzyme could be induced increased to elimate excess ROS. Contens of reactive oxide species, superoxide anion, hydroxyl radical, hydrogen peroxide, were all first increased and then decreased and at last increased again. This change was fit with the change of SOD and CAT. It was proved that, excess ROS was produced under exposure of respective DEP, DAP, DBP, BBP. Inhibitors of electron transfer chain were added to find the site where PAEs act on in K. brevis cells. Results showed that the site of DEP acted was the electron transfer chain of mitochondria, the site of DAP and DBP acted were both the electron transfer chain of mitochondria and chloroplast, the site of BBP acted was the electron transfer chain of chloroplast. The conculusions were proved by detected the content of hydroxyl radical in isolated mitochondria and chloroplast. Results showed that, in isolated chloroplast, as control, content of hydroxyl radical was obviously increased under exposure of DAP, DBP, BBP, repectively. And in isolated chloroplast, as control, content of hydroxyl radical was obviously increased under exposure of DEP, DAP, DBP, repectively.