Poster Presentation Annual Meetings of the Endocrine Society of Australia and Society for Reproductive Biology and Australia and New Zealand Bone and Mineral Society 2016

Acute exposure to environmental concentrations of the endocrine disruptor atrazine affects preimplantation bovine embryo total cell count but not development or quality (#477)

Ashleigh J Henderson 1 , Bethany J Finger 1 , Alexandra J Harvey 1 , Mark P Green 1
  1. School of BioSciences, University of Melbourne, Melbourne, VIC, Australia

Exposure to endocrine disruptors can have many negative health implications. Atrazine, the most widely used pesticide worldwide, has been identified as an endocrine disruptor. Atrazine studies have largely examined long-term exposure at supra-environmental concentrations on the whole organism, while few studies have investigated effects on the preimplantation embryo at environmentally-relevant concentrations. Therefore, the aim of this study was to determine whether acute, environmentally-relevant exposure to atrazine affected preimplantation embryo development, quality, and metabolism. Bovine oocytes (n=3662) were matured in vitro, fertilised, then cultured in ESOF medium until d3.5. Embryos that had reached at least the 8-cell stage (n=1480) were divided into LSOF groups in the presence of 0.002% DMSO (control), 0.02ng/mL atrazine (low; Australian waterways level), or 0.02µg/mL atrazine (high; NH&MRC-approved safe concentration). On d7.5 embryos were assessed for development and quality, then differentially stained to assess cell numbers. Alternatively, embryos were cultured individually from d6.5 to d7.5 in metabolic LSOF supplemented with their respective treatments, with resulting blastocysts assessed for stage, grade and total cell number. Resultant spent media were analysed for glucose consumption and lactate production. Development, cell number, and metabolism data were analysed by ANOVA using a PROC MIXED procedure in SAS.

Embryo development and quality were not affected by atrazine (P>0.1). However, the presence of atrazine decreased total cell number (P<0.05, n=245), within low (154.4±4.1, P=0.02, n=78), and high (156.4±3.8, P=0.08, n=90) atrazine treated embryos, relative to control (167.1±4.1, n=77). Despite this, no effect of atrazine was evident on inner cell mass or trophectoderm cell numbers, or their ratio (P<0.1). Ongoing metabolic assessment may reveal perturbed carbohydrate utilisation in the presence of atrazine. These data demonstrate that even acute, environmentally-relevant exposure to atrazine during the preimplantation window can have subtle effects on embryo characteristics. Such perturbations may have long-term consequences post-implantation.