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Functional roles of ionic currents in a membrane delimited sino-atrial node (SAN) cell model were investigated. Ionic currents were blocked and intracellular calcium ([Ca 2+ ]i) buffered to study their effects on action potential (AP) characteristics. The simulations revealed that blocking the hyperpolarization activated current and the T-type calcium current caused an increase of cycle length (CL) due to reduced diastolic depolarization rate (DDR). Blocking of sustained outward (I st ) and sodium currents ( INa,1.1 , I Na,1.5 ) had no effect. Blocking the L-type calcium current's Cav1.3 isoform (I CaL1.3 ) and rapidly activating delayed rectifier arrested pacemaking. Blocking sodiumcalcium exchanger (I NaCa ) caused a CL reduction but did not affect DDR. Reducing [Ca 2+ ] i increased CL marginally. A small increase of [Ca 2+ ] i arrestedpacemaking. I st , I Na1.1 , and I Na1.5 are not functional and I NaCa is a background current in the model.

Type

Journal article

Journal

Computing in Cardiology

Publication Date

01/12/2010

Volume

37

Pages

421 - 424