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 degreesC 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+.