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

1 Using the whole cell configuration of the patch clamp technique, we studied the potential blocking effects of gadolinium (1 mu M to 1 mM) on potassium currents: I-KR, I-KS and I-K1. The study was performed on guinea-pig isolated ventricular myocytes. 2 The background current, I-K1 was insensitive to Gd3+. Thus, we found that no obvious screening of surface charges was visible with concentrations of Gd3+ up to 100 mu M. 3 By use of three different protocols: tail currents fitting, analysis of envelope of tails and electrophysiological dissection, we found that I-KR was the only component of I-K that was sensitive to Gd3+. The sensitivity was apparently different depending on the protocol used. 4 Comparison of the results obtained with the different protocols revealed that the rapid component of I-KR is more sensitive to Gd3+ than the slow one. 5 Of the different protocols used to distinguish between I-KR and I-KS, the electrophysiological dissection seems to be the more accurate.