Pharmacological modulation of ion channels and transporters

Ion channels and transporter proteins are prerequisites for formation and conduction of cardiac electrical impulses. Acting in concert, these proteins maintain cellular Na(+) and Ca(2+) homeostasis. Since intracellular Ca(2+) concentration determines contractile activation, we expect the majority of agents that modulate activity of ion channels and transporters not only to influence cellular action potentials but also contractile force. Drugs which block ion channels usually possess antiarrhythmic properties, those inhibiting the Na(+) pump have predominantly inotropic effects and those affecting Na(+),Ca(2+)- or Na(+),H(+)-exchanger protect against ischaemic cell damage. However, irrespective of their primary indication, all compounds targeted against ion channels and transporter proteins possess potential proarrhythmic activity.