Ca 2+ Flux Through Promiscuous Cardiac Na + Channels: Slip-Mode Conductance

Publisher Website
Google Scholar
Abstract
The tetrodotoxin-sensitive sodium ion (Na + ) channel is opened by cellular depolarization and favors the passage of Na + over other ions. Activation of the β-adrenergic receptor or protein kinase A in rat heart cells transformed this Na + channel into one that is promiscuous with respect to ion selectivity, permitting calcium ions (Ca 2+ ) to permeate as readily as Na + . Similarly, nanomolar concentrations of cardiotonic steroids such as ouabain and digoxin switched the ion selectivity of the Na + channel to this state of promiscuous permeability called slip-mode conductance. Slip-mode conductance of the Na + channel can contribute significantly to local and global cardiac Ca 2+ signaling and may be a general signaling mechanism in excitable cells.