In vitroinduction/inhibition of germinal vesicle breakdown (GVBD) in frog (Euphlyctis cyanophlyctis) oocytes by endocrine active compounds

Abstract

Oocyte maturation is transformation of oocytes into a fertilizable egg. This study examined the effects of four classes of chemicals: 1) acephate (organophosphate); 2) atrazine (herbicide); 3) cypermethrin and fenvalerate (synthetic pyrethroids); and 4) carbaryl (carbamate) on in vitro germinal vesicle breakdown (GVBD) of Euphlyctis cyanophlyctis oocytes. Follicles were isolated and defolliculated from surgically removed ovaries of E. cyanophlyctis and exposed to either progesterone (1 μM/mL) or graded concentrations (1, 5, 10, 15, and 20 μg/mL) of test chemicals. GVBD was evident by the presence of a white spot in the animal pole as well as the absence of germinal vesicles in sectioned heat-fixed oocytes. Percent GVBD was scored every 4 hours until 24 hours. Progesterone induced 77-84% GVBD, compared to 29-33% in controls, at 24 hours. Acephate induced 46-67% GVBD, whereas atrazine elicited 58-77% of GVBD. In cypermethrin or carbaryl- or fenvalerate-exposed oocytes, GVBD was limited to 22-28, 17-29 and 18-24%, respectively. The study infers that some chemical contaminants in the aquatic system may interfere with GVBD in amphibians. Because oocyte maturation is a prerequisite for the production of fertilizable eggs, any alteration in this process potentially impairs the fecundity of females.

Toxic effects of atrazine on porcine oocytes and possible mechanisms of action

“…Our results indicate that just as in other models, in our experimental model, atrazine has direct toxic effects on porcine oocytes in vitro [23, 25]. Similar results have been reported in porcine oocytes, namely, that treatment with atrazine decreases oocyte meiotic maturation [36].…”

“…A few studies have shown toxic effects of atrazine on oocyte quality in vitro in Xenopus frogs and Japanese medaka models [23–25]. These studies have revealed that atrazine is detrimental to oocyte maturation; however, the mechanisms of toxicity are still not clear.…”

Environmental (anti-)androgenic chemicals affect germinal vesicle breakdown (GVBD) of Xenopus laevis oocytes in vitro

“…Numerous studies have described effects of EDCs on gonadal differentiation, the secondary sex characteristic development, and metamorphic process of amphibians (Crump et al, 2002;Hayes et al, 2002Hayes et al, , 2010Porter et al, 2011;Qin et al, 2003). Also, some of EDCs, such as ethinyl estradiol, atrazine, 2,4-dichlorophenoxyacetic acid and methoxychlor, have been shown to affect oocyte maturation in amphibians, suggesting potential adverse effects on reproductive function of amphibians (Fort et al, 2002;Ghodageri and Katti, 2013;Pickford and Morris, 1999;Stebbins-Boaz et al, 2004). Given that androgens can induce oocyte maturation and anti-androgen flutamide can inhibit androgen-induced oocyte maturation, we propose that environmental androgens and anti-androgens could disrupt oocyte maturation of amphibians.…”

Effects of atrazine on fish, amphibians, and reptiles: update of the analysis based on quantitative weight of evidence

“…In the course of the analysis, two papers overlooked during the development of the original WoE assessment were identified and analyzed. In the end, the papers included in the QWoE update are: (Chang et al 2005;Hecker et al 2005;Svartz et al 2012;Ghodageri and Katti 2013;Olker 2014;Shenoy 2014;Baxter et al 2015;Chen et al 2015;Sai et al 2015Sai et al , 2018Syngenta 2015Syngenta , 2017aSyngenta , 2017bVan Der Kraak et al 2015;Wirbisky and Freeman 2015;dos Santos Mendonc¸a et al 2016;Ehrsam et al 2016;Gustafson et al 2016;Khan et al 2016aKhan et al , 2016bKhan et al , 2016cLiu et al 2016;Richter et al 2016;Russart and Rhen 2016;Tulaby Dezfuly and Mohammadian 2016;Wirbisky et al 2016aWirbisky et al , 2016bWirbisky et al , 2016cD'Angelo and Freeman 2017;Du Gas et al 2017;Hoskins et al 2017;Jones et al 2017;Khalil et al 2017;Kirsten et al 2017;McMahon et al 2017;Persch et al 2017;Scott et al 2017;Shukla et al 2017;Snyder et al 2017;Wang et al 2017;…”

“…There were three new studies on the effects of atrazine on in vitro cultures of tissue, one for an amphibian and two for fish ( Figure 24). Atrazine at concentrations of 1000 to 20,000 mg/L was reported to induce breakdown of germinal vesicle in the ovarian follicles of the frog (Euphlyctis cyanophlyctis) (Ghodageri and Katti 2013). All these concentrations were not environmentally relevant.…”