In Vitro Testing of the Insecticide Reldan 22 on Swine Oocyte Maturation

Abstract

Chlorpyrifos (Reldan 22®) is an widely used insecticide for the control of insect pests in agriculture and in residential areas. It is classified as moderately toxic by the United States Environmental Protection Agency and has been quantified in human biological fluids. Our aim was to test the toxicity of Chlorpyrifos (Reldan 22 ® ) and investigate its effects in an in vitro model using swine oocyte maturation. Swine oocytes from ovaries harvested in a commercial slaughterhouse were cultured for 44-45h in M199 supplemented with the following Reldan 22 ® concentrations: 0.1, 0.5, 1 or 2 µl/ml. Cumulus oophorous expansion was assessed and oocytes were denuded and stained with 1 µg/ml fluorescein diacetate to estimate viability. Afterwards, oocytes were fixed in a 60% methanol in DPBS solution and stained with 50 µg/ml propidium iodide to observe the DNA stage. Our research shows that the Reldan 22 ® insecticide stimulated cumulus expansion to an extent but reduced oocyte viability which was accompanied by an increase in the number of immature oocytes and a decrease in the percentages of gametes that resumed meiosis. This leads us conclude that its presence in the oocyte environment is toxic for development at concentrations 0.5, 1 and 2 µl/ml.