Saheli Kumar, Soumyadip Panja, Abhishek Choudhury, Adity Sarbajna, Suman Bhusan Chakraborty
ABSTRACT The present study emphasizes the cAMP‐dependent signaling pathway, germinal vesicle breakdown (GVBD), and the role of the Nrf2–metallothionein (MT) system under metal‐induced oxidative stress. It compares how zinc (Zn) and lead (Pb) affect steroid‐driven oocyte maturation in the freshwater catfish Mystus vittatus via in vitro exposure of oocytes to inhibitory concentrations (1/10 IC₅₀: ZnSO₄ at 3.9 μM, Pb (NO₃) 2 at 2.4 μM). Measurements included reactive oxygen species, Ca 2+ , cAMP‐protein kinase A, maturation‐inducing hormone (MIH), MT, estradiol receptor α, cyclin B–Cdc2, and the nuclear factor erythroid 2‐related factor 2 and Kelch‐like ECH‐associated protein 1 pathway. Exposure of oocytes to Zn and Pb significantly ( p < 0.05) reduced GVBD, MIH, and Ca 2+ levels, whereas estradiol and ERα remained unchanged. Pb exposure significantly ( p < 0.05) elevated cAMP and PKA. Cyclin B and Cdc2 protein levels significantly ( p < 0.05) dropped in metal‐exposed oocytes. Both metals significantly ( p < 0.05) increased ROS, with Pb inducing greater. MT and nuclear Nrf2 expression increased significantly ( p < 0.05), whereas cytosolic Keap1 significantly ( p < 0.05) declined, most markedly with Pb. Statistical analyses, including ANOVA, correlation, principal component analysis (PCA), and random forest model (RFM), were performed to understand the redox‐regulatory mechanisms of the oocyte maturation pathway in distinct, metal‐specific ways: Pb more strongly impaired steroid‐mediated oocyte maturation than Zn. PCA and RFM highlighted increased ROS, Nrf2, cAMP, and MT, with decreased MIH–MPF components, indicating that metal‐induced redox activation up‐regulated the Nrf2–MT pathway while suppressing maturation signals, thereby delaying oocyte maturation.