One of the transgenic crops widely used both in agriculture and in the food industry is genetically modified soybean (GTS 40-3-2) with the new Roundup Ready trait. This transgenic soybean is resistant to Roundup herbicide due to the introduced gene of the Agrobacterium tumefaciens bacterium. The GM-soybean synthesizes bacterial 5-enolpyruvylshikimat-3-phosphate synthase (EPSPS) replacing the herbicide-inhibited enzyme in the plant, hence, after Roundup herbicide application in the field, the transgenic soybean continues to grow, whereas weeds die. The widespread use of Roundup Ready transgenic soybean and Roundup herbicide gives rise to concern about their safety for the environment, as well as animal and human health.
The thesis is devoted to the study of the long-term effects of glyphosate-resistant genetically modified soybean untreated and treated with Roundup herbicide and of the herbicide itself on female rat reproduction for two generations, on rat postnatal development and massometric parameters, on protein metabolism indicators (alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltransferase, creatinine, urea, uric acid and total protein) in tissues, urine and blood of three rat generations. The content of carbonyl derivatives in tissues of three rat generations and the state of their antioxidant protection system (concentrations of superoxide dismutase, catalase, glutathione and glutathione-dependent enzymes) were studied as one of the criteria for safety assessment of genetically modified organisms.
The thesis has confirmed the negative effects of Roundup herbicide and transgenic soybean GTS 40-3-2 treated with herbicide on both structure and function of rat kidneys and livers, namely, causing reversible cellular swelling in kidney and liver cells, which is the most pronounced in the third rat generation. It has also been shown that soybean seeds are able to accumulate the herbicide, which can be partially neutralized by heat treatment. Long-term use of both the GM soybean treated with the herbicide and the herbicide itself has been found to lead to an increase in mortality of the next two rat generations, especially for rats aged up to two months. In addition, the changes in their massometric parameters (an enlargement of liver mass among the experimental groups), especially in the F1 and the F2 generations of rats were established.
Analysis of biochemical data of rat blood and liver obtained during carrying out the thesis work confirms the hepatocytes structure disruption, namely, some damage to their cell membranes, as evidenced by an increase in aminotransferase level in the blood (especially alanine aminotransferase). An increase in the De Ritis Ratio (alanine aminotransferase/aspartate aminotransferase ratio) indicates the liver origin of this enzyme. Some changes in other biochemical parameters, in particular, a rise in the level of average mass molecules in blood (indicator of intoxication) prove the toxicity of this herbicide.
The studies of the carbonyl derivatives level, SH-groups content and the proteolytic enzymes activity have showed an increase in the protein oxidative modification, subsequently, the proteins become sensible to proteolysis. The obtained results testify to the rise in the number of reactive oxygen species, contributing to the initiation of free radical processes in the liver and kidney cells of the rats received the herbicide with drinking water and the rats fed with soybean seeds, containing the herbicide residues. The depletion of antioxidant protection system and the oxidant-antioxidant system imbalance have been also observed. The glutathione peroxidase and glutathione transferase activities also decreased in blood, liver, and kidneys of the rats received the Roundup herbicide with drinking water and of the rats fed with transgenic soybean treated with herbicide. The decrease was more pronounced for the F1 and F2 generations of rats. For the rats fed with untreated transgenic soybean the antioxidant protection enzymes activity remains almost unchanged compared to the control group.
