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Abstract
However pesticides are contributing to dramatic increase in crops yields and helping to limit the spread of certain diseases through controlling pests, they are hazardous for human, animals and environment. The present study aimed to investigate the toxopathological effects of methomyl, one of the most used carbamate pesticides in agriculture in Egypt, on albino rats. In which, one hundred and thirty male rats, three months old and 200-300g weight, were obtained from Faculty of Medicine, Assiut University. Animals were treated according to two experimental protocols, short and long-term exposures. In short-term exposure, forty rats were divided into four groups (10 rats each) that treated for one week. In the first group, rats were received one dose of methomyl (10 mg/kg b.w., 1/2 LD50) in distal water on the first day of treatment. Methomyl was given as a single oral dose (2 ml) by stomach tube. In the second group, rats were received methomyl as in group A. Additionally, Nigella sativa oil was given three times weekly, on Saturday, Thursday and Friday, at a dose of 2 ml/kg b.w. by stomach tube. In the third group, rats were received methomyl as in group A. Additionally, rats were received green tea polyphenols (900 mg/L) in drinking water during the whole time of experiment. In the fourth group, rats were received one dose of distilled water by stomach tube on the first day of treatment and kept as a control for animals in groups 1. In long-term exposure, ninety rats were divided into six groups that treated for three months. In the first group, twenty rats were received methomyl at a dose of 2 mg/kg b.w. (1/10 LD50) in distal water. Methomyl was given three times weekly, on Saturday, Monday and Wednesday, by stomach tube. In the second group, twenty rats were received methomyl as in group A. Additionally, Nigella sativa oil was given at a dose of 2 ml/kg b.w. three times, 3 h after methomyl intubation, by stomach tube. In third group, twenty rats were received methomyl as in group A. Additionally, rats were received green tea polyphenols (900 mg/L) in drinking water for 3 days/week. In fourth group, ten rats were received distilled water, 3 times/week by stomach tube and kept as a control for animals in group 1. In fifth group, ten rats were received only Nigella sativa oil at a dose of 2 ml/kg b.w. three times weekly by stomach tube. Animals were kept as a control for group 2. In group six, ten rats were received only green tea polyphenols (900 mg/L) in drinking water for 3 days/week. Animals were kept as a control for group 3. At the end of each treatment, animals were sacrificed by cervical dislocation and blood samples and tissue specimens were taken for hematological and biochemical parameters and histopathological examinations, respectively.
Clinical signs
Clinical signs were only obvious after treatment of animals with a single dose of methomyl in the form of mild seizures. These seizures appeared within 1 – 2 min and lasted for half hour and then disappeared. Seizures appeared to be due to inhibition of AChE by methomyl.
Hematological pictures
Treatment of rats with a single dose of methomyl only increased the total numbers of WBCs compared to control animals. Treatment of methomyl-treated rats with Nigella sativa oil and green tea polyphenols for one week increased the total numbers of WBCs by 55% and 59%, respectively. Exposure of animals to methomyl for 3 months decreased the total numbers of RBCs and WBCs and Hb concentration by 13%, 34% and 13%, respectively. Nigella sativa oil and green tea polyphenols were found to increase the total numbers of WBCs and Hb concentration by 23% and 10%, respectively, compared to methomyl-treated animals.
Biochemical measurements
Treatment with a single dose of methomyl significantly decreased albumin levels by 16% compared to control animals. No significant effects were produced on the levels of total proteins, albumin and globulin as a result of treatment with Nigella sativa oil or green tea polyphenols. Methomyl significantly increased albumin levels and consequently decreased globulin levels by 42% and 61%, respectively, after three months of exposure. Nigella sativa oil and green tea polyphenols significantly increased globulin levels by 46% and 53%, respectively, compared to methomyl-treated rats. The levels of urea and creatinine were significantly increased by 52% and 107%, respectively, after treatment of rats with single dose of methomyl. Treatment with Nigella sativa oil and green tea polyphenols significantly decreased urea and creatinine levels by 32% and 55%, and 39% and 106%, respectively, compared to methomyl-treated rats. Similarly, treatment of rats with methomyl for three months significantly increased urea and creatinine levels by 127% and 75%, respectively, compared to control animals. Nigella sativa oil was only found to decrease creatinine levels by 69% compared to methomyl-treated rats.
Histopathology
Histopathological changes were obvious in the brain, liver, kidneys, lungs, testicles and spleen. They were more pronounced after three months of methomyl exposure. Examination of brain sections revealed neuronal degeneration and necrosis particularly in the hippocamupus, cerebrum and cerebellum and microglial proliferation. Liver showed degeneration of hepatocytes, focal areas of necrosis, activation of Kupffer’s cells, apoptotic changes and increase the mitotic figures. Kidneys had glomerular swelling, periglomerular fibrosis and degeneration of the tubular epithelial lining. Lungs revealed alveolar emphysema, exfoliation of bronchiolar epithelial cells and thickening of alveolar septa. There was also hyaline degeneration of blood vessel walls with perivascular mononuclear accumulation. Testicular lesions consisted of degeneration of testicular epithelial cells, sloughing of cells in the tubular lumina and formation of giant cells. Splenic lesions were marked lymphocytic depletion and presence of hemosiderin-laden macrophages within splenic trabiculae. Treatment with Nigella sativa oil or green tea polyphenols markedly decreased the intensity and prevalence of the lesions in different organs compared to methomyl-treated animals.
However pesticides are contributing to dramatic increase in crops yields and helping to limit the spread of certain diseases through controlling pests, they are hazardous for human, animals and environment. The present study aimed to investigate the toxopathological effects of methomyl, one of the most used carbamate pesticides in agriculture in Egypt, on albino rats. In which, one hundred and thirty male rats, three months old and 200-300g weight, were obtained from Faculty of Medicine, Assiut University. Animals were treated according to two experimental protocols, short and long-term exposures. In short-term exposure, forty rats were divided into four groups (10 rats each) that treated for one week. In the first group, rats were received one dose of methomyl (10 mg/kg b.w., 1/2 LD50) in distal water on the first day of treatment. Methomyl was given as a single oral dose (2 ml) by stomach tube. In the second group, rats were received methomyl as in group A. Additionally, Nigella sativa oil was given three times weekly, on Saturday, Thursday and Friday, at a dose of 2 ml/kg b.w. by stomach tube. In the third group, rats were received methomyl as in group A. Additionally, rats were received green tea polyphenols (900 mg/L) in drinking water during the whole time of experiment. In the fourth group, rats were received one dose of distilled water by stomach tube on the first day of treatment and kept as a control for animals in groups 1. In long-term exposure, ninety rats were divided into six groups that treated for three months. In the first group, twenty rats were received methomyl at a dose of 2 mg/kg b.w. (1/10 LD50) in distal water. Methomyl was given three times weekly, on Saturday, Monday and Wednesday, by stomach tube. In the second group, twenty rats were received methomyl as in group A. Additionally, Nigella sativa oil was given at a dose of 2 ml/kg b.w. three times, 3 h after methomyl intubation, by stomach tube. In third group, twenty rats were received methomyl as in group A. Additionally, rats were received green tea polyphenols (900 mg/L) in drinking water for 3 days/week. In fourth group, ten rats were received distilled water, 3 times/week by stomach tube and kept as a control for animals in group 1. In fifth group, ten rats were received only Nigella sativa oil at a dose of 2 ml/kg b.w. three times weekly by stomach tube. Animals were kept as a control for group 2. In group six, ten rats were received only green tea polyphenols (900 mg/L) in drinking water for 3 days/week. Animals were kept as a control for group 3. At the end of each treatment, animals were sacrificed by cervical dislocation and blood samples and tissue specimens were taken for hematological and biochemical parameters and histopathological examinations, respectively.
Clinical signs
Clinical signs were only obvious after treatment of animals with a single dose of methomyl in the form of mild seizures. These seizures appeared within 1 – 2 min and lasted for half hour and then disappeared. Seizures appeared to be due to inhibition of AChE by methomyl.
Hematological pictures
Treatment of rats with a single dose of methomyl only increased the total numbers of WBCs compared to control animals. Treatment of methomyl-treated rats with Nigella sativa oil and green tea polyphenols for one week increased the total numbers of WBCs by 55% and 59%, respectively. Exposure of animals to methomyl for 3 months decreased the total numbers of RBCs and WBCs and Hb concentration by 13%, 34% and 13%, respectively. Nigella sativa oil and green tea polyphenols were found to increase the total numbers of WBCs and Hb concentration by 23% and 10%, respectively, compared to methomyl-treated animals.
Biochemical measurements
Treatment with a single dose of methomyl significantly decreased albumin levels by 16% compared to control animals. No significant effects were produced on the levels of total proteins, albumin and globulin as a result of treatment with Nigella sativa oil or green tea polyphenols. Methomyl significantly increased albumin levels and consequently decreased globulin levels by 42% and 61%, respectively, after three months of exposure. Nigella sativa oil and green tea polyphenols significantly increased globulin levels by 46% and 53%, respectively, compared to methomyl-treated rats. The levels of urea and creatinine were significantly increased by 52% and 107%, respectively, after treatment of rats with single dose of methomyl. Treatment with Nigella sativa oil and green tea polyphenols significantly decreased urea and creatinine levels by 32% and 55%, and 39% and 106%, respectively, compared to methomyl-treated rats. Similarly, treatment of rats with methomyl for three months significantly increased urea and creatinine levels by 127% and 75%, respectively, compared to control animals. Nigella sativa oil was only found to decrease creatinine levels by 69% compared to methomyl-treated rats.
Histopathology
Histopathological changes were obvious in the brain, liver, kidneys, lungs, testicles and spleen. They were more pronounced after three months of methomyl exposure. Examination of brain sections revealed neuronal degeneration and necrosis particularly in the hippocamupus, cerebrum and cerebellum and microglial proliferation. Liver showed degeneration of hepatocytes, focal areas of necrosis, activation of Kupffer’s cells, apoptotic changes and increase the mitotic figures. Kidneys had glomerular swelling, periglomerular fibrosis and degeneration of the tubular epithelial lining. Lungs revealed alveolar emphysema, exfoliation of bronchiolar epithelial cells and thickening of alveolar septa. There was also hyaline degeneration of blood vessel walls with perivascular mononuclear accumulation. Testicular lesions consisted of degeneration of testicular epithelial cells, sloughing of cells in the tubular lumina and formation of giant cells. Splenic lesions were marked lymphocytic depletion and presence of hemosiderin-laden macrophages within splenic trabiculae. Treatment with Nigella sativa oil or green tea polyphenols markedly decreased the intensity and prevalence of the lesions in different organs compared to methomyl-treated animals.