Rapid effects of cytochalasin-D on contraction and intracellular calcium in single rat ventricular myocytes

Contraction and intracellular calcium ([Ca²⁺](i)) transients were recorded using a video edge detector and fluorescence spectrophotometry, respectively, in rat ventricular myocytes at 22-24°C stimulated at a frequency of 1 Hz. Application of the F-actin disrupter cytochalasin-D (Cyt-D) caused a large reduction in the amplitude of contraction and a small increase in the [Ca²⁺](i) transient. These responses began within a few seconds of application and were complete after 2 min of exposure. Phase-plane relationships of contraction and [Ca²⁺](i) were consistent with cytochalasin-D causing a decrease in myofilament responsiveness to Ca²⁺.