Inhibition of oocyte maturation by organophosphate insecticides in zebrafish (Danio rerio) after in vitro and in vivo exposure

Oogenesis is the process by which a primary oocyte develops into a fertilizable oocyte. During the final step in zebrafish (Danio rerio) oogenesis, oocyte maturation, the maturation inducing hormone 17α,20β-dihydroxy-4-pregnen-3-one (MIH) activates the membrane progesterone receptor (mPR), inducing germinal vesicle breakdown. Anthropogenic stressors can dysregulate oocyte maturation. However, it is unknown waterborne exposure to chemicals that perturb maturation after in vitro exposure also disrupt MIH induced maturation in vitro, or if the in vitro assay is predictive of reproductive performance. Here, we demonstrate that malathion and dimethoate inhibit oocyte maturation when oocytes are exposed in vitro or in vivo, suggesting that the in vitro zebrafish oocyte maturation assay might be predictive of alterations to reproductive performance. This research introduces the oocyte maturation assay as being predictive of the success of in vitro oocyte maturation after in vivo exposure, but it remains unclear whether this assay is predictive of reproductive impairment.Alberta Innovates Technology Futures, Canada research chairs Tier 2:35224, NSERC Discovery:RGPIN 2017 04474, Canada first excellence research funds