Protective Role of Purslane Supplementation Against Cadmium-Induced Renal and Gill Toxicity in Nile Tilapia: Insights into Antioxidant Defense and Ion Transport Regulation.

Cadmium chloride (Cd) is a hazardous heavy metal known to impair antioxidant defenses and disrupt ion regulation in aquatic organisms. This study investigated the protective role of purslane (Portulaca oleracea, PUR), a medicinal plant rich in antioxidant bioactives, against Cd-induced oxidative stress and ion transporter dysfunction in Nile tilapia (Oreochromis niloticus). One hundred and eighty fish were divided into four groups (3 replicates per group, 15 fish/replicate): control, PUR (1% dietary inclusion), CdCl₂ (50 µg/L), and CdCl₂ + PUR, and exposed for 60 days. CdCl₂ exposure significantly elevated serum urea, uric acid, creatinine, glucose, and cortisol levels (by 67%, 20%, 78%, 54%, and 202%, respectively; P < 0.001), along with hypocalcemia (↓21%), hypermagnesemia (↑103%), and reduced serum iron (↓73%). Antioxidant enzyme activities in the gills were markedly suppressed (GPx (↓67%), CAT (↓67%), and SOD (↓61%)), with a depletion of GSH (↓58%) and an elevation of MDA (↑55%). The corresponding mRNA expressions of these enzymes in the kidney were downregulated (3.7-6.7-fold; P < 0.001). CdCl₂ also upregulated heat shock proteins hsp60, hsp70, and hsp90 in the  kidney (5.7-8.4-fold; P < 0.001), indicating oxidative and cellular stress. Histopathological examination revealed pronounced tissue damage in the kidney and gill structures. Ion regulation was also disrupted by CdCl₂, as evidenced by reduced gill Ca