A binding-site model for calcium channel inactivation that depends on calcium entry.
We describe a model for the mechanism by which Ca channel inactivation might depend on calcium entry. Ca is assumed to bind to a site at the internal membrane surface to cause inactivation of Ca channels. We assume that Ca that enters through the membrane accumulates in a submembrane compartment and also make simplifying assumptions about Ca buffering and removal. Our model predicts the results of single- and double-pulse voltage-clamp experiments well. The predicted turn-off of Ca current is non-exponential. The model also predicts that procedures that slow inactivation will increase peak Ca current and suggests that both two-phase turn-off of currents and failure of normalized current to recover to 1.0 in two-pulse experiments may be explained without assuming a voltage-dependent component of inactivation or two populations of Ca channels.
D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology; D004553:Electric Conductivity; D006801:Humans; D007473:Ion Channels / Q000187:drug effects*; D008564:Membrane Potentials; D008954:Models, Biological
D007473:Ion Channels; D002118:Calcium