Flash4.0 lt camera

Freshly isolated ventricular myocytes were placed in normal Tyrode's solution containing (in mM): 137 NaCl, 5.4 KCl, 0.16 NaH₂PO₄, 10 glucose, 1.8 CaCl₂, 0.5 MgCl₂, 5.0 HEPES, and 3.0 NaHCO₃ (pH adjusted to 7.4 with NaOH) and paced to steady state using a 1 Hz field stimulation. After 20 s of stimulation, the cells showed steady contractions, and video images were acquired using a Flash4.0 LT camera by line scanning (4 ms line⁻¹, C11440‐42U, Hamamatsu, Japan). Image J was used to measure the cell length under contraction (systolic length) and relaxation (diastolic length). Cardiomyocyte sarcomere shortening, which reflects the contractility of cardiac muscles, was calculated as (diastolic length–systolic length)/diastolic length × 100%. Measurements were taken from more than 20 myocytes from three or more animals from each group.

Isolated cardiomyocytes were placed in a thermostat and stimulated by 1 Hz electric field to achieve a steady state. After 20 s of stimulation, cardiomyocytes showed stable contraction. Video images of cardiomyocyte contraction process at 4 ms were acquired by line scanning using a Flash4.0 LT camera (4 ms/line; C11440-42U; Hamamatsu, Japan). HCImageLive and Image J were used to measure cardiomyocyte length during systole and diastole. Cardiomyocytes shortening = (diastolic length – systolic length) / diastolic length × 100%.