Joint Toxicity Of Chlorobenzenes And Heavy Metals To Tetrahymena And Mechanism Study

In this paper, microcalorimetry was used to study the single toxicity and joint toxicity on Tetrahymena, the accumulation of intracellular heavy metals was studied by ICP-AES, damage of the cell membrane and change of function groups was studied by ATR-FTIR spectra, the cell surface damage on the control of the compounds was observed by SEM, and then, the mechanisms of toxicity was explored. The main results and conclusions are summarized as follows:1. The toxicity of five chlorobenzenes to Tetrahymena growth metabolism was studied by microcalorimetry. And the growth constant (k) decreases with the increasing of drug concentration, indicating that the growth metabolism had been inhibited. The results suggest that the order of toxicity is 1,2,4-trichlorobenzene> o-dichlorobenzene> p-dichlorobenzene> m-dichlorobenzene> chlorobenzene.These five compounds half-inhibition concentrations are 21,30,37,38,45 mg/L. Biological microscopy was used to observe the membrane damage slowly, morphology change significantly, until internal material spill. It reflected drugs changed the permeability of cell membrane. ATR-FTIR spectra showed that under the action of chlorobenzenes, the amine and PO2 peak change significantly, and some peaks disappeared, indicating that certain compounds can cause the cell membrane damage.2. The toxicity of three heavy metals to Tetrahymena growth metabolism was studied by microcalorimetry. And the growth constant (k) decreased with the increasing of metals concentrations, indicating that the growth metabolism had been inhibited. The results suggest that the order of toxicity is Cd2+>Cr3+>Cu2+.These three metals half-inhibition concentrations are 150,0.405,100 mg/L. By ICP-AES results showed that:with the increase in the amount of added metal ions, Tetrahymena cells also increased the amount of metal ions, but it has decreased after reaching a maximum value, indicating that the enough metal ions damaged the cell membrane permeability, both inside and outside cells metal ions happened the exchange. Tetrahymena with the molecular structure of cell membranes, ATR-FTIR spectra showed that under the action of chlorobenzenes,the amine and PO2peak changed significantly, and some peaks disappeared, indicating that certain metal ions damaged the cell membrane.3. The joint toxicity of five chlorobenzenes and three heavy metals to Tetrahymena growth metabolism was studied by microcalorimetry. Under the combined effect, k was also increased with the reduction of mixture concentrations, the inhibition rate I gradually increased. Different joint compounds, different degrees of inhibition, with the same metal ions, and different chlorobenzenes, were not the same degree of inhibition. The joint toxicity was evaluated using Additive Index method. The results showed that the studied system was all synergies. By ATR-FTIR study showed that under the action of joint drug, the amine and PO2-peak of the phospho-lipid phospho-diester, both in the hydrophobic end exposed to the outer layer were changed significantly, and some peaks disappeared, indicating that certain drugs on the cell membrane damage. And damage was significantly stronger than a single toxic. Surface of the cell membrane of Tetrahymena micro-situation was observed by FE-SEM, the role of drugs found to be significant after the empty cells; the cells have sufficient time to a large degree of damage.4. The toxicity of chlorobenzene compounds in a quantitative structure-activity relationship was studied, QSAR model is constructed:logIC50 =- 0.378logKOW +0.476 ELOMO-0.618â–³QÏ€R-1.804 (n= 5, R= 0.706, SE= 0.132). Mechanism of toxicity of chlorobenzenes compounds, mainly happened in the sugar and protein molecules of the-SH,-NH-and other pro-nuclear groups, they damage the cell membrane phospholipids and glycoproteins, chlorobenzenes through the cell membrane into the cells, and then transfer charge with macromolecules, thus affecting the normal metabolism of cells; excess copper and chromium metal will form a protein, nucleic acid complexes, when these were excessive, metal caused toxic effects. synergy type of joint toxicity may be due to both co-exist in vivo, the formation of metals complex, chelate, and a metal protease, can promote the chlorobenzene substances into the target, so fast destruction the permeability of cell membranes, resulting in toxic strengthened.