Cytochalasin D Alters Kinetics of Ca2+Transient in Rat Ventricular Cardiomyocytes: An Effect of Altered Actin Cytoskeleton?

The effects of cytochalasin D, a specific F-actin depolymerizing agent, on Ca2+transients in rat ventricular cardiomyocytes were investigated. Cytochalasin D (20μ ) significantly slowed decay of Ca2+transients (τdecaycontrol CELLS=28.1±1.3,n=28τdecay=47.3±2.8 ms,n=20,P<0.001). The rising phase of Ca2+transients was also significantly slower in cytochalasin D treated cells (τrise=5.1±0.6 ms,n=17vτrisein control CELLS=3.6±0.2,n=21,P<0.01). Phalloidin (100μ ), an F-actin stabilizer, prevented cytochalasin D-induced alterations of Ca2+transient kinetics. The cytochalasin D effect was not related to the -type Ca2+current since the current density and kinetics were not altered by the drug. We conclude that integrity of F-actin-based cytoskeleton is an important factor for sarcoplasmic reticulum function.