Oxidative Stress and Ca2+ Signals Involved on Cadmium-Induced Apoptosis in Rat Hepatocyte

Cadmium (Cd) is an important industrial and environmental pollutant. In animals, the liver is the major target organ of Cd toxicity. In this study, rat hepatocytes were treated with 2.5 similar to 10 mu M Cd for various durations. Studies on nuclear morphology, chromatin condensation, and apoptotic cells demonstrate that Cd concentrations ranging within 2.5 similar to 10 mu M induced apoptosis. The early-stage marker of apoptosis, i.e., decreased mitochondrial membrane potential, was observed as early as 1.5 h at 5 mu M Cd. Significant (P < 0.01) reactive oxygen species (ROS) production at 5 mu M Cd and 0.75 h occurred prior to the decrease of the mitochondrial membrane potential, suggesting the involvement of ROS in mitochondrial membrane damage. Glutathione (GSH) level significantly decreased after cell treatment with 5 and 10 mu M Cd after 12 h (P < 0.01). Meanwhile, the intracellular free Ca2+ concentration ([Ca2+] (i) ) of Cd-exposed cells significantly increased (P < 0.01) at 1.5 h, and pretreatment with the calcium chelator Bapta-AM partially blocked Cd-induced apoptosis. This finding indicated that the elevation of [Ca2+] (i) may play an important role in apoptosis. Overall, these results showed that oxidative stress and Ca2+ signaling were critical mediators of the Cd-induced apoptosis of rat hepatocytes.