DELAYED RECTIFIER CURRENT ASSAYS

SINGLE VENTRICULAR MYOCYTES

EFFECTS OF SOTALOL ON THE DELAYED RECTIFIER CURRENT IKr

Figure 1 Effects of sotalol on the delayed rectifier current IKr.

Figure 1 shows superimposed currents records elicited by a 40 ms and 400 ms step depolarisation to +40 mV in the absence (black) and presence (red) of sotalol (100 鮍
Membrane currents were recorded under standard conditions for the measurement of native IK in single left ventricular myocytes using high resistance microelectrodes and the swirch-clamp technique.

Outward tail current elicited after a 40 ms step depolarisation which accurately reflects IKr is abolished by sotalol. 
However, tail currents elicited after a 400 ms step depolarisation which reflect both IKr and IKs  were only partially inhibited by sotalol. 

 
 

Figure 2  Effects of sotalol on IKrand IKs.

 
 

Figure 2   Sotalol-induced prolongation of the action potential is mediated in part via inhibition of IKr.
These data (illustrated in Figure 2) show that the amplitude of the tail current activated after 40 ms, IKr, was significantly reduced by 75ॠby sotalol.  However, the amplitude of the tail current elicited after 400 ms, comprising both IKs and IKr, was only reduced by 39ॠreflecting the contribution of IKr to this current.

These data suggest the the effects of sotalol are mediated via and effects on IKr rather than on IKs.

 
   
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