Toxicity And Estrogen Effects Of Dicofol To Bufo Gargarizans

Abstract: Dicofol is a kind of organochlorine insecticide, which is widely used by modern animal breeding and agriculture production. Recent years, more and more researches indicated that dicofol exposing in the environment would have toxicity and estrogen effects on Fishes, Reptiles, Aves, Mammals, and even humans. Yet there is no experimental reports about Amphibian. Bufo gargarizans, the species of Bufonidae in Anura, is an important economic animals in our country, and distributes in many kinds of living conditions with different altitude in more than 20 provinces of our country. They inhabit in the moist places such as farmlands, orchards, brushwood, vegetable fields, hurst or aroud the human resident. B. gargarizans with features of euryphage and hearty eater, is one of the principle natural enemies of many agriculture pests. With the experimental material of B. gargarizans, the paper investigated the acute toxicity and estrogen effects that dicofol have on the tadpoles and the adults of toad, meanwhile dicussed the mechanism of these biological effects, which would provide more evidences about the researches on the toxcity and estrogen effects of dicofol on the Amphibian, and give the basic materials of protecting the wild animal resources and human food safety.The adults of toad bought from doumen laboratory animal culture plant Xi'an city, the tadpoles collected from Duqu town of Chang'an County. Select 80 healthy adults weighing 55-115 g and 300 tadpoles aged 18-22 days for acute toxicity experiment;select 28 healthy adults weighing 65-85 g and 160 tadpoles aged 25 days for estrogen effects experiment. In estrogen effects experiment, the adults were dealt with 5 concentration gradient of dicofol and the tadpoles were dealt with 7 concentration gradient of dicofol respectively as disturbing team;and with physiological brine and estradiol as the two control team. With the methods of histology and immunohistology, the influence of dicofol effect on the structure of sexual gland was observed and the effect on the expression of testosterone and androgen receptors was detected. From the experiment results, discussion and analysis, the paper reaches the following conclusions:1. On the condition of 15-25℃ room temperature, injecting dicofol into the adult of toad. After 48 hours, the absolute lethal concentration(LC₁₀₀) of dicofol affected on the male and female of the adults of toad is respectively 300 mg.kg^-1 and 400 mg.kg^-1, the maximal tolerance concentration(LC₀) is respectively 100mg.kg^-1 and 120 mg.kg^-1,the medican lethal concentration(LC5o) is respectively 161.27+19.34 mg.kg'1 and 188.51+20.93 mg.kg"1. The result indicated that the resistance ability of the male adult toad to dicofol was poorer than that of the female.2. On the condition of 12-18 °C and 18-25°C, exposing in dicofol for 48 hours, the LCioo of dicofol effected on the tadpoles is respectively 15.0 mg.l"1 and 3.5 mg.l"1, the LCois respectively 6.0 mg.l"1 and 1.0 mg.l"1, the LC50 is respectively 8.64 + 0.97 mg.l"1 and 2.45 + 0.28 mg.l'1. The result showed that in certain a range of temperature, the toxicity of dicofol effected on the tadpoles would aggravated with the rising of the temperature.3. Certain a range of concentration of dicofol would lead to some tadpoles abnormalllity and lagged development. Furthermore, the tadpoles dealt with the concentration of 0.016, 0.04, 0.08, 0.16 mg.l*1, there were more females than males.4. Certain a range of concentration of dicofol had strong inhibitory effects on the development of oocytes in the female adults of B. gargarizans, which would lead different degree of follicle atresia. The result showed that dicofol may have toxicity effects on the development of oocytes in female adults. Furthermore, certain a range of concentration of dicofol also had inhibitory effects on the expression of testosterone and androgen receptors in oocytes, which we can concluded that the dicofol maybe have estrogen or antiandrogen effects.5. Certain a range of concentration of dicofol would make the structure of Seminiferous tubule, Spermatogonium, Leydig cells shrinked, and the quantity of sperm decreased. And that, the influence expanded with the increasing of the concentration. Moreover, dicofol had reduced the expression of testosterone and androgen receptors in the testis of male adults, and the reducing degree of testosterone expression was much more apparent than that of androgen receptors. The result indicated that Certain a range of concentration of dicofol would lead the hypofunction of testis in male adults, and the mechanism may be that dicofol had restrained the expression of testosterone.6. Certain a range of concentration of dicofol also had bad influence on the ovary of tadpoles of B. gargarizans, which would result in abnormal phenomenon such as the shrink of the oocytes nucleus, and disturb the normal process of oocytes development. Furthermore, dicofol also had inhibitory effects on the expression of testosterone and androgen receptors, and the reducing degree of testosterone expression was much more apparent than that of androgen receptors. The result showed that the main mechanism of the estrogen effect of dicofol was to directly restrain the expression of testosterone.7. Certain a range of concentration of dicofol had repressing influence on the structure of Seminiferous tubule and Leydig cells of tadpoles of B. gargarizans, and the influence expanded with the increasing of the concentration. Alike, dicofol reduced the expression of testosterone and androgen receptors, and the inhibitory degree of testosterone expression was much more apparently. The results can be concluded that the estrogen effects of dicofol achieved by the way of directly restraining the expression of testosterone.