Biochemical Responses in Zebra Fish (Danio rerio) on Acute Cadmium Exposure Under Temperature Variations

Increased urbanization and human activities have led to global warming and the discharge of heavy metals into water. With this background, the current study was aimed to assess the effect of cadmium (Cd) upon acute exposure (3–8 mg/L) and increasing temperature (18–34 °C) using zebra fish (Danio rerio), a representative small indigenous freshwater fish. Changes in glucose, total protein, free and conjugated bilirubin, cholesterol, triglycerides, and heat shock proteins in hepatic tissue homogenate supernatant were measured to understand the toxicological effects of these two stressors. Among different biochemical parameters, glucose level exhibited a highly significant increase (p < 0.05) in fishes maintained at 34 °C and exposed to Cd (416 ± 02 mg/L) compared to the control group (276 ± 13 mg/L). At higher temperatures, zebrafish mortality due to cadmium exposure increased, indicated by a lower median lethal concentration. This was accompanied by a notable increase in the expression of heat shock proteins 70 and 90. The study confirms that temperature is a potent environmental factor confounding cadmium toxicity.