Thin filament activation by phalloidin in skinned cardiac muscle.
Phalloidin binds very tightly and specifically to actin and brings about a marked stabilization of the F-actin filament. In this study the effects of phalloidin on force generation and Ca2+ sensitivity of skinned bovine ventricular muscle were investigated. At all free Ca2+ concentrations addition of phalloidin to activated fibers caused an enhancement of active force. At full Ca2+ activation the force increase was about 6% and the relative force enhancement became greater as the Ca2+ concentration was decreased. Force-pCa plots obtained with fibers pre-treated with phalloidin showed that phalloidin produced an approximately 0.2 pCa unit increase in Ca2+ sensitivity without significant changes in cooperativity of activation. These results suggest that interactions between G-actin subunits may play an important role in cardiac force development.
Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, PA 15261, USA.
A E
AE
Bukatina
F
F
Fuchs
P W
PW
Brandt
D000199:Actins / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002417:Cattle; D006321:Heart / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism; D010590:Phalloidine / Q000633:toxicity*; D016276:Ventricular Function
D000199:Actins; D010590:Phalloidine; D002118:Calcium