Atrazine and diazinon inhibit oocyte maturation and ovulation in zebrafish

Oocyte maturation and ovulation are well characterized biological processes in fish that are induced by progestins through the coordination of nongenomic actions via the membrane progesterone receptor (mPR) and genomic actions via the nuclear progesterone receptor (Pgr). In zebrafish, the effects of chemicals on these processes can be elucidated using in vitro and in vivo oocyte maturation and ovulation assays. The binding affinity of chemicals for mPR and Pgr can be analyzed using a recently established graphene quantum dot (GQD)-labeled mPR and Pgr binding assay. Combining these physiological and biochemical analyses makes it possible to investigate whether the effects of chemical substances on oocyte maturation and ovulation are mediated by mPR and Pgr. In this study, the effects of herbicides and pesticides on fish oocyte maturation and ovulation were evaluated using in vitro and in vivo assays. The findings revealed that at concentrations greater than 0.1 μM, atrazine (ATZ) and diazinon (DZN) substantially reduced oocyte maturation, whereas 2,4-D exposure did not have a similar effect. ATZ and DZN reduced oocyte maturation and ovulation in vivo. However, the concentrations of these compounds required to inhibit ovulation were significantly lower than those required to inhibit oocyte maturation. The binding affinity of endocrine-disrupting chemicals (EDCs) was analyzed using GQD-labeled mPR and Pgr binding assays. All three EDCs-ATZ, DZN, and 2,4-D-exhibited binding affinity for mPR. For Pgr, DZN and 2,4-D exhibited binding affinity, but ATZ did not. These results suggest that ATZ and DZN prevent fish oocyte maturation and ovulation by binding to mPR.