PT  - JOURNAL ARTICLE
AU  - Pascal Daleau
AU  - Majed Khalifa
AU  - Jacques Turgeon
TI  - Effects of Cadmium and Nisoldipine on the Delayed Rectifier Potassium Current in Guinea Pig Ventricular Myocytes
DP  - 1997 May 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 826--833
VI  - 281
IP  - 2
4099  - http://jpet.aspetjournals.org/content/281/2/826.short
4100  - http://jpet.aspetjournals.org/content/281/2/826.full
SO  - J Pharmacol Exp Ther1997 May 01; 281
AB  - Block of the slow inward calcium current (Isi) during assessment of the delayed rectifier potassium current (IK) of cardiac ventricular myocytes is commonly achieved by use of either inorganic compounds such as cadmium or dihydropyridine derivatives such as nisoldipine. Effects of these two Isi blockers on IK characteristics of guinea pig ventricular myocytes were compared in this study. Currents were measured in the whole cell configuration of the patch-clamp technique and IK tail amplitudes were measured at −40 mV after depolarizations to various test potentials (voltage steps, −20 to +50 mV) for either 250 (IK250), 450 (IK450) or 5000 (IK5000) msec. Activating and tail currents measured in the presence of cadmium were of greater amplitudes when voltage steps were more positive than 0 mV but were of smaller amplitudes at Vtest ≤ 0 mV compared to currents measured in the presence of nisoldipine or Tyrode solution. In the presence of the rapid component of the delayed rectifier E-4031, a blocker of cadmium increased IKs amplitude during high voltage tests and caused a positive shift in the voltage dependence of IKsactivation at low depolarizing potentials. In contrast, no effect on IK was observed when nisoldipine was added to Tyrode solution. In conclusion, results obtained in this study suggest that cadmium depresses and/or shifts the activation curve of the rapid component and increases and positively shifts the slow component of IK in guinea pig ventricular myocytes. These observations lead us to propose that nisoldipine may be a better tool to inhibit long lasting inward calcium current during assessment of IK. The American Society for Pharmacology and Experimental Therapeutics