Effects Of Malathion On Reproductive Toxicology Of Male Rats

Malathion is widely used in agriculture production because of its high efficiency and relatively low acute toxicity compared to other OP insecticides and induces adverse effects on the environment and human health. Long term exposure to malathion, dichlorvos, omethoate and other organic phosphorus pesticide will produce reproductive damage of different degrees on experimental animals. This study aimed to investigate the reproductive toxicity of malathion on testes in male rats. To examine the activity ofacetylcholine esterase (AchE), the histological changes in testis and sperm quality, the activities of testicular enzymes and measured the hormone levels including luteinizing hormone (LH), follicle-stimulating hormone(FSH) and testosterone (T) using radioimmunoassay (RIA). We further assessed the expression levels of genes related to reproduction.ObjectiveTo investigate the toxicity of malathion on the reproductive system of male rats and provide evidence and clues for the study of toxic effect and mechanism caused by malathion.MethodsAfter 1 week of acclimatization,40 male Wistar rats of SPF (Specific Pathogen Free) quality weighing between 80 and 100 g were randomly divided into four groups including three exposure groups and a control group of 10 animals each. In the exposure groups, the rats were exposed to malathion by oral gavage at dosages of 33.75 mg/kg(1/32LD50)、 54mg/kg(1/2OLD50)、108mg/kg(1/10LD50) daily for 60 days:The control rats were administered with an equivalent volume of distilled water in the same manner. Throughout the experimental period, all animals were observed at least once daily for clinical signs of toxicity related to malathion exposure.After the last exposure, the rats were sacrificed by cervical dislocation, then immediately take the testis and epididymis, observe its shape and quickly stripped adipose tissue, weighed the weight of testes and epididymis. The left epididymis of each rat was collected, and the caudal epididymis was used to prepare sperm suspension for measuring sperm counts, motility, and dysmorphology rate. Testicular tissue was prepared to detect the activities of enzymes (ACP, LDH, SDH, y-GT). The right testis tissues were stained with hematoxylin and eosin (HE) for light microscopic examination. The apoptotic cells were detected using a TUNEL assay kit and immunohistochemistry was conducted according to SABC kits instructions. Blood samples were taken from the retinal vein to detect AchE, LH, FSH and T levels.ResultsThe body, testis and epididymis weights significantly decreased in rats treated with 54 and 108 mg/kg malathion (P< 0.01). Sperm count and motility in the caudal epididymis of rats exposed to malathion were lower than that in the control rats. Statistical differences were found in rats treated with higher concentration of malathion (108 mg/kg) when compared with that in the control group (P< 0.01). The rates of sperm dysmorphology in rats from 54 and 108 mg/kg groups were statistically higher than that in the control rats (P< 0.01).The results indicated that the activities of ACP and y-GT of rats in the 108 mg/kg group were significantly lower than that in the control group (P< 0.01). Activities of LDH were significantly higher in the same treated-rats compared to the control rats (P< 0.01). Hormone levels decreased in the treatment groups and rats treated with 108 mg/kg of malathion showed significant decreases of LH, FSH and T compared with that in the control group. The activity of AchE was significantly decreased in rats treated with 108 mg/kg of malathion(P<0.05).Histological examination showed malathion dosed at 54 and 108 mg/kg resulted in severe alterations in the seminiferous tubules including the loss, derangement and sloughing of the spermatogenic cells, vacuolization in Sertoli cell cytoplasm and destruction of Sertoli cell cytoskeleton.The apoptosis rate was increased significantly in malathion-treated groups compared to the control group (P<0.01). The number of Bax positive staining was increased with increasing dosage of malathion and the gray value was significantly decreased at 54 and 108 mg/kg groups compared to the control group (P< 0.01). The number of Bcl-2 positively-stained cells decreased and the gray value was significantly increased at 54 and 108 mg/kg groups (P< 0.05).Conclusion1. The study suggests that malathion had a negatively effect on the reproduction of male rats and inhibit the activity of AchE.2. Malathion could change the activities of enzymes (ACP, LDH, SDH, y-GT) and inhibit spermatogenesis of male rats.3. Malathion could decrease the hormone levels (LH, FSH and T) and interfere with the normal function of the endocrine system of male rats.4. Malathion could cause testis pathological damage and result in spermatogenic failure of male rats.5. Malathion could lead to spermatogenic cell apoptosis and change the expression levels of apoptosis-related proteins.6. Malathion produce reproductive toxicity on male rats.