Effects of Humic Acid on Liver and Kidney Toxicity Induced by Cadmium in Brown Trout (Salmo trutta fario, L)

This study was conducted to determine the histopathological and biochemical effects of humic acid on cadmium stress in liver and kidney tissues of Salmo trutta fario, L. The fish were treated in four groups as follows and were exposed to chemicals for 7 days: control (C), cadmium (2 ppm) (Cd), humic acid (5 ppm) (HA) and humic acid + cadmium (Cd + HA). At the end of the experimental period, liver and kidney samples were taken from all fish for histopathological examination and determination of antioxidant enzyme (glutathione peroxidase, superoxide dismutase) and malondialdehyde (MDA) levels. Activity of GPx and SOD in the tissues of fish exposed to the stress of Cd was significantly lower than the control groups (P<0.05). MDA level increased (P<0.05) in cadmium exposed groups, whereas fish receiving cadmium with humic acid returned to normal MDA levels in the liver. The cadmium-induced histopathological alterations were also decreased with humic acid. These results suggest that humic acid may mediate cadmium toxicity.