Influence of triazine herbicide exposure on guppies (poecilia sphenops) aromatase activities, altered sex steroid concentration and vitellogenin induction
Byline: S. Vasanth, G. Arul, S. Karthikeyeni, TSV. Kumar, V. Vignesh, M. Manimegalai, G. Bupesh, R. Thirumurugan, P. Subramanian
Atrazine, a herbicide is one the most toxic and sustaining pollutants in aquatic environment. It is detectable in surface water and in underground sources of drinking water. Many studies indicate that atrazine might be a potent endocrine disrupting xenobiotic. There are limited studies have revealed that the effects of atrazine on sex steroids hormones, vitellogenin and induction of aromatase, gonadosomatic index and hepatosomatic index. In this study, juvenile Poecilia sphenops fish was exposed to three different (0.83, 1.25 and 2.5 ppm) concentration of atrazine for 100 d. Changes in plasma and gonadal content and concentrations of sex steroids and vitellogenin protein in poecilia sphenops under laboratory conditions were assessed. The low level of the atrazine show estrogenic effect in males, as determined by a shortage of testosterone induction. Present study suggests that low induction of plasma vitellogenin and aromatase in male fish become suitable biomarkers of exposure to estrogenic chemicals.
Herbicides are extensively used in agriculture, sanitation, gardens and weed control. Terrestrial and aquatic environments are mainly polluted by indiscriminately used agriculture products [sup] . They contaminate the food chains and display toxic effects in animals and the human population. In the last 60 years, atrazine (2-chloro-4-ethylamino- 6-isopropylamino-s-triazine) has been one of the most extensively used herbicides in agriculture and roadways which, has been considered as an endocrine disruptor, causing adverse effects on reproductive function mainly by altered sex hormone levels and gonadal abnormalities [sup],,,, . Possible interactions of atrazine with numerous endocrine functions have been the subject of various studies [sup],,,,, .
Environmental compounds that disrupt endocrine function have been associated to adverse effects on the reproductive system in wildlife and humans. Although there are several mechanisms through which, environmental chemicals might alter the endocrine system, chemicals that mimic steroid hormones through an interaction with the estrogen receptor continue to receive considerable attention. Numerous environmental chemicals can bind to the estrogen receptor and initiate transcription of the estrogen receptor regulated genes in vitro [sup] .
Induction of vitellogenin protein in male fish has been extensively used as a biomarker for exposure of xenoestrogens in field and in laboratory studies. Vitellogenin (VTG) is a yolk precursor protein produced in the liver under the stimulation of ovarian estradiol and is normally found in female blood, whereas VTG levels in male fish are normally very low or absent [sup] . However, if exposed to an exogenous estrogen, male fish are capable to synthesis VTG protein equivalent to that of mature female fish [sup], . The enzyme aromatase, (P450 arom), is a member of the P450 cytochrome family complex and encoded by the CYP19 gene. The aromatase enzyme converts testosterone (T) to estradiol (E2) and is found in the brains of most male and female vertebrates. The enzyme is important for male sexual behaviour in a variety of species including rodents [sup], . The aromatization of androgens to estrogens takes place in the endoplasmic...