MTBE Hormesis On Cell Proliferation And Its Toxicological Significance

Research Aim:To study whether Methyl Tertiary Butyl Ether (MTBE) has hormesis on cell proliferation and how its dose-effect relationship is. At the same time to investigate the safe dose of MTBE in the environment.Methods:1. The MTT test was used to detect the cytotoxic effect of MTBE in Human Bronchial epithelial cells (16HBE cells). At the same time to observe whether MTBE could induce 16HBE cells to occur hormesis and determine its dose range (Hormetic Zone).2. Us Single cell gel electrophoresis to observe whether the MTBE within the dose of Hormetic Zone can lead to DNA damage in 16HBE cells.3. Set several dose groups of MTBE within the dose of Hormetic Zone. Let the mice continuously be exposed to these groups of MTBE by way of drinking for three months. Then detecte the DNA damage in their whole blood cells and leucocytes by SCGE while test the DNA damage in their bone marrow reticulocytes using micronucleus test.Result1. MTT test revealed that MTBE could induce 16HBE cells to occur hormesis and its dose range of Hormetic Zone is 1 g/L～10 g/L.2. SCGE experiment showed that apoptosis take place in most 16HBE cells after exposed to 40g/L dose of MTBE for 4h. Each index value in MTBE dose groups of lg/L～30g/L is higher than that in normal control group. It revealed that lg/L～30g/L doses of MTBE can cause DNA damage in 16HBE cells. It also showed clear dose-effect relationship.3. After continuous exposure to each dose group of MTBE for 90 days, the whole blood cells, leucocytes of blood and bone marrow reticulocyte were collected from the mice. We used these tissues to carry out related experiments. SCGE test showed that MTBE can result in DNA damage in whole blood cells and reticulocyte at the dose of 2.5～5g/L, and it also showed clear dose-effect relationship. Compared with the normal control group, no significant difference has been found in each exposure group (including male and female mouse) about the PCE/NCE value. It demonstrated that long-time exposure to low-dose MTBE is harmless to hematopoiesis. There was no significant difference between the normal control group and each exposure group about the micronucleus rate. Only at the dose of 1.25g/L, the micronucleus rate of female mice was significantly increased compared with the normal control group. Micronucleus test revealed that the dose of MTBE set in this experiment cannot cause chromosome damage.Conclusion:1. MTBE could induce 16HBE cells to occur hormesis on proliferation and its dose range of Hormetic Zone is 1 g/L～10 g/L.2. 1g/L～10g/L doses of MTBE can cause DNA damage in 16HBE cells and shows clear dose-effect relationship.2.5～5g/L doses of MTBE can cause DNA damage in whole blood cells and reticulocytes and has dose-effect relationship.2.5～5g/L doses of MTBE have no significant influence on PCE/NCE value and micronucleus rate. Accordingly, we think that the doses of MTBE in Hormetic Zone is dangerous to organisms, can cause slight DNA damage, but cannot lead to serious damage such as Chromosome breakage.