Different effects of gadolinium on IKR, IKS and IK1 in guinea‐pig isolated ventricular myocytes

Abstract
Using the whole cell configuration of the patch clamp technique, we studied the potential blocking effects of gadolinium (1 μM to 1 mM) on potassium currents: IKR, IKS and IK1. The study was performed on guinea‐pig isolated ventricular myocytes. The background current, IK1 was insensitive to Gd3+. Thus, we found that no obvious screening of surface charges was visible with concentrations of Gd3+ up to 100 μM. By use of three different protocols: tail currents fitting, analysis of envelope of tails and electrophysiological dissection, we found that IKR was the only component of IK that was sensitive to Gd3+. The sensitivity was apparently different depending on the protocol used. Comparison of the results obtained with the different protocols revealed that the rapid component of IKR is more sensitive to Gd3+ than the slow one. Of the different protocols used to distinguish between IKR and IKS, the electrophysiological dissection seems to be the more accurate.