F-actin modulates swelling-activated chloride current in cultured chick cardiac myocytes.
The integrity of F-actin and its association with the activation of a Cl- current (I(Cl)) in cultured chick cardiac myocytes subjected to hyposmotic challenge were monitored by whole cell patch clamp and fluorescence confocal microscopy. Disruption of F-actin by 25 microM cytochalasin B augmented hyposmotic cell swelling by 51% (from a relative volume of 1.54 +/- 0.10 in control to 2.33 +/- 0.21), whereas stabilization of F-actin by 20 microM phalloidin attenuated swelling by 15% (relative volume of 1.31 +/- 0.05). Trace fluorochrome-labeled (fluorescein isothiocyanate or tetramethylrhodamine isothiocyanate) phalloidin revealed an intact F-actin conformation in control cells under hyposmotic conditions despite the considerable changes in cell volume. Sarcoplasmic F-actin was very disorganized and occurred only randomly beneath the sarcolemma in cells treated with cytochalasin B, whereas no changes in F-actin distribution occurred under either isosmotic or hyposmotic conditions in cells treated with phalloidin. Swelling-activated I(Cl) (68.0 +/- 6.0 pA/pF at +60 mV) was suppressed by both cytochalasin B (22.7 +/- 5.1 pA/pF) and phalloidin (22.5 +/- 3.5 pA/pF). On the basis of these results, we suggest that swelling of cardiac myocytes initiates dynamic changes in the cytoarchitecture of F-actin, which may be involved in the volume transduction processes associated with activation of I(Cl).
Zhang
J
J
Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Larsen
T H
TH
Lieberman
M
M
D000199:Actins / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D018118:Chloride Channels / Q000502:physiology*; D003571:Cytochalasin B / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004553:Electric Conductivity; D005456:Fluorescent Dyes; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D007038:Hypotonic Solutions; D007700:Kinetics; D018613:Microscopy, Confocal; D009206:Myocardium / Q000166:cytology; D010590:Phalloidine / Q000494:pharmacology; D012508:Sarcolemma / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure
D000199:Actins; D018118:Chloride Channels; D005456:Fluorescent Dyes; D007038:Hypotonic Solutions; D010590:Phalloidine; D003571:Cytochalasin B; D004121:Dimethyl Sulfoxide