Toxic Effects of Co‐Exposure of Dibutyl Phthalate and Cadmium Chloride on the Ovary of Adult Zebrafish: Evaluation of Oxidative Stress Parameters and Histopathology

Dibutyl phthalate (DBP) and cadmium chloride (CdCl₂) are environmental contaminants with endocrine-disrupting properties that adversely affect reproductive and neurological functions in aquatic organisms. This study investigated the toxicological effects of DBP and CdCl₂ co-exposure on adult female zebrafish (Danio rerio) ovary for 28 days. Zebrafish were divided into five groups: control, vehicle control, DBP (1 mg/L), CdCl₂ (1 mg/L), and a combined DBP + CdCl₂ group (each at 1 mg/L). Biochemical analysis revealed significant reductions in superoxide dismutase (SOD) activity and total antioxidant capacity (TAC) across all treatment groups, with catalase (CAT) activity decreasing in the DBP and combined exposure groups. Conversely, malondialdehyde (MDA) levels were significantly elevated in the combined exposure group, indicating enhanced oxidative stress. Gene expression analysis showed down-regulation of sod in the DBP and combined groups, cat in the combined group, and nrf2 across all treatments reflecting compromised antioxidant defense pathways. Histopathological analysis revealed higher number of peri-nuclear oocytes (PO), degenerated mature oocytes (DMO), and yolk granule depletion (DYG) in DBP-exposed group. While, CdCl₂-exposed group showed degenerated cortical alveolar oocytes (DCO), DMO, and DYG. However, the combined exposure group exhibited more pronounced damage, including a higher number of atretic peri-nuclear oocytes (APO) and more pronounced DMO and DYG, indicating severe ovarian dysfunction. DBP exposure led to a significant increase in pre-vitellogenic oocytes and a significant reduction in mature oocyte diameter. Overall, these findings demonstrate that DBP and CdCl₂ exposure induce oxidative stress, impair antioxidant gene expression, and cause significant histomorphological alterations in the zebrafish ovary, highlighting their potential to disrupt reproductive health in aquatic species.