Measurement of intracellular ATP

Intracellular ATP levels in cells were measured using a firefly luciferase-based ATP assay kit (Beyotime, China) in accordance with the manufacturer’s instructions. Briefly, cardiomyocytes were lysed and subjected to centrifugation at 10,000 × g for 10 min at 4 °C. An equal volume (50 μl) of supernatant from each group was mixed with 50-μl luciferin/luciferase reagent to catalyze the light production from ATP and luciferin. Chemiluminescence was measured with a fluorescence microplate reader. Intracellular levels of ATP were normalized to protein concentrations (Edwards et al. 2018).