Determination of intracellular Ca2+ levels
In accordance with the instructions of commercial kits, the productions of Ca2+ in cardiomyocytes and differentiated skeletal myoblasts treated with PA and/or samples were evaluated with a fluo-8AM probe. The cell medium was discarded, and PBS solution containing 4 μM of fluo-8AM was added to the cells for 45 min incubation. Calcium production in each group was imaged by a fluorescent microscope (Olympus CKX53, Tokyo, Japan).