Effects Of Atrazine On Reproductive Development Of Zebrafish, Brachydanio Rerio

Atrazine (2-chloro-4-ethylamino-6-isopropylamine-s-triazine, ATR) is a widely used selective herbicide to control broadleaf weeds and gramineous grasses. The presence of atrazine in water and soil environment is a major concern because atrazine may be a potential carcinogen and maintains toxicity over a long period of time. To understand fully the effects of atrazine on the reproductive development of zebrafish, histological observation on hypothalamus, pituitary and gonad in company with gonadal hormone analyse were conducted after zebrafish exposed to difference atrazine concentrations. Acute toxicity experiments of atration on zebrafish embryos and larvae were also conducted.1. The embryos and larvae of zebrafish were significantly affected by atrazine. With the increasing of atrazine concentration, hatchability was reduced, malformation rate and lethality of juvenile were increased. The lethality and malformation rate of embryos were increased when atrazine concentration was higher than 30 mg/L. All of the embryos were dead when the atrazine concentration was 50 mg/L. Larval zebrafish was also sensitive to the toxicity of atrazine, the 24 h LC50 was 36.25 mg/L, and the 48 h LC50 was 22.89 mg/L. After 48 hour of exposure at the atrazine concentration of 50 mg/L, all the zebrafish larvae dead.2. Atrazine inhibited gonadal development significantly in zebrafish, The degree of gonadal development had negative correlation to the concentration of atrazine.That is, the higher the concentration of atrazine, the maturity of gonadal cells to reduce, the more delayed gonadal development, and this phenomenon will be more obvious under longer term exposure to atrazine. The estrogen effective had a positive correlation with the concentration of atrazine With the increase of atrazine concentration and exposure time, the number of zebrafish ovarian increase. However, the conclusions are not obvious on hypothalamus and pituitary by histological study.3. Atrazine has a certain degree of interference effect on hormone balance of zebrafish. The content of E2 raised in zebrafish tissue fluid with the increasing of atrazine concentration. Compared with the control group(E2 concentration:7.84 pmol/L), when the concentration of atrazine was 10-4,10-3 mg/L, the E2 concentrations increased a bit, and when the concentration of atrazine was 10-2,10-1,1 mg/L, the E2 concentrations in zebrafish tissue fluid increased over 100%, it reached 41.44 pmol/L when the concentration of atrazine was 1 mg/L. Compared with the control group(T concentration:0.064 ng/ml), the T concentrations in zebrafish tissue fluid increased with varying degrees, but there was no obvious gradient changes, all were 0.1-0.15 ng/ml. E2/T ratio also showed the same trend with E2, when the concentration of atrazine increased to 1 mg/L, E2/T ratio increased significantly. The results show that, the concentration of 1 mg/L is possible the point which can cause the reaction to atrazine for zebrafish.To sum up, atrazine as one of endocrine disruptors, can inhibit gonadal development in zebrafish, and raise the lethality and malformation rate of zebrafish embryos and juvenile. Therefore, atrazine can affect the reproductive development of zebrafish obviously, so it should be used with caution.