4.1.3. Oxygen Consumption Ratio (OCR) Measurement

The OCR in cardiomyocytes was measured using a MitoXpress® probe (Cayman Chemicals, Ann Arbor, MI, USA) according to the manufacturer's instructions. Cells were plated at <sup>2</sup> × <sup>10</sup><sup>4</sup> cells/well in 96-well plates and incubated with SpD at 37 ◦C and 5% CO2 for 24 h. After replacing the spent media with 160 μL of 10% FBS-DMEM containing SpD, 10 μL of MitoXpress® Xtra Solution, and 100 μL of mineral oil were added to all wells. The plates were incubated at 37 ◦C and 5% CO2 for 10–20 min and then the fluorescence was read at 380 nm excitation/650 nm emission on a fluorometer with a delay time of 100 μs (SpectraMax M2e).
