This study was to examine the effects of copper on the mitochondrial non-specific pore. Three hundred sixty, one-day-old, healthy Arbor Acres (AA) broilers were fed with different concentrations (11, 110, 220, and 330 mg/kg) of copper originated from copper sulfate, tribasic copper chloride (TBCC), or copper methionine. At the indicated time point, the mitochondrial permeability transition (MPT) and copper concentration were analyzed. Results showed that under the same copper concentration, the MPT of broilers fed copper methionine was the greatest, followed by TBCC, then copper sulfate. The effects of copper on MPT were time- and dose-dependent. Furthermore, in vitro in the presence of K(+), 5 μM Cu(2+) could cause permeability transition as compared to 10 μM Cu(2+) in buffer without K(+). Taking these results together, we have shown that hepatocellular MPT may be influenced not only by source and concentration of copper or the raising period of broilers, but also by the existence of K(+).