The Effect of a Novel Highly Selective Inhibitor of the Sodium/Calcium Exchanger (NCX) on Cardiac Arrhythmias in <i>In Vitro</i> and <i>In Vivo</i> Experiments - Fig 10

<p><b>Panel A.</b> The effect of 1 μM ORM-10962 on the delayed afterdepolarization (DAD) amplitude in dog right ventricular Purkinje fibres. DAD was evoked by a 40 stimulus train with a stimulation cycle length of 400 ms in the presence of 150 nM digoxin. Trace <b>a</b> is a control recording, trace <b>b</b> indicates the induction of DAD by 150 nM digoxin, and trace <b>c</b> demonstrates that 1 μM ORM-10962 almost completely abolished DAD. <b>Panel B.</b> Effect of ORM-10962 (1 μM) on digoxin-induced automaticity in dog right ventricular Purkinje fibres. Trace <b>a</b> is a control recording. Spontaneous activity was recorded after a 40 stimulus train with a stimulation cycle length of 400 ms in the presence of 150 nM digoxin (trace <b>b</b>). Application of 1 μM ORM-10962 in the presence of digoxin abolished the spontaneous activity (trace <b>c</b>).</p

The Effect of a Novel Highly Selective Inhibitor of the Sodium/Calcium Exchanger (NCX) on Cardiac Arrhythmias in <i>In Vitro</i> and <i>In Vivo</i> Experiments - Fig 12

<p><b>Panel A</b>. Effect of ORM-10962 (0.3 mg/kg) in ischemia-reperfusion induced ventricular arrhythmias during reperfusion after 6 min coronary artery ligation in anesthetized (pentobarbitone, 60 mg/kg <i>i</i>.<i>p</i>.) rats. Time to the development of ventricular arrhythmias was measured on the ECG. The ordinates show the numbering of the animals. There was no significant change in the arrhythmias following administration of ORM-10962. <b>Panel B.</b> Effect of ORM-10962 (1 μM) in global ischemia-reperfusion induced ventricular fibrillation in isolated guinea pig hearts. ORM-10962 did not influence significantly the duration of ventricular fibrillation.</p

Effect of ORM-10962 (0.3 mg/kg) on ouabain (10 μg/kg/min i.<i>v</i>.) induced arrhythmias in anesthetized (pentobarbitone, 45 mg/kg <i>i</i>.<i>p</i>.) guinea-pigs.

<p><b>Panel A</b>. ORM-10962 was applied as a pre-treatment 10 min before starting permanent ouabain infusion. Mean time to the development of ventricular arrhythmias is indicated on the Figure. <b>Panel B.</b> ORM-10962 was administered after the termination of 16 min ouabain infusion. In both <b>Panels</b> the ordinate indicates the numbering of the animals. There was a considerable antiarrhythmic effect; the duration of arrhythmic periods was shorter under the influence of ORM-10962.</p

Determination of NCX current in dog ventricular myocytes.

<p>The protocol was adapted from Hobai <i>et al</i> [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0166041#pone.0166041.ref027" target="_blank">27</a>]. <b>A:</b> Recording obtained with the voltage protocol shown in the inset in control conditions (current trace after blockade of Na⁺, Ca²⁺, K⁺ and Na⁺/K⁺ pump currents. <b>B:</b> The current trace after superfusion with 100 nM ORM-10962. <b>C:</b> The current trace at the end of the measurements after the application of 10 mM NiCl₂. On the right the control NCX current is shown, which is obtained by subtracting trace <b>C</b> from trace <b>A</b>. The NCX current in the presence of 100 nM ORM-10962 is obtained by subtracting trace <b>C</b> from trace <b>B</b>. Note the difference in the intensity-time calibration in the left and right panels.</p

The concentration-dependent effect of ORM-10962 on the NCX current in dog ventricular myocytes.

<p><b>Panel A</b>. Original Ni²⁺-sensitive (NCX) current traces before and after superfusion of the cells with ORM-10962 at concentrations of 10 nM, 100 nM and 1 μM. <b>Panel B.</b> The drug-response curve of ORM-10962 on the outward (top) and inward (bottom) NCX currents in dog ventricular myocytes is given at 20 mV and at -80 mV, respectively. Values are means ± SEM. Numbers in brackets show the number of experiments for each data point.</p

Lack of effect of ORM-10962 on the inward rectifier potassium and transient outward potassium currents (I_K1 and I_to) in dog ventricular myocytes.

<p><b>Panels A and B.</b> Original I_K1 (top) and I_to (bottom) current traces (left panels) recorded under control conditions and in the presence of 1 μM ORM-10962, and the corresponding I-V current-voltage relationships (right panels) before and after application of 1 μM ORM-10962, respectively. The insets in the I-V diagrams show the voltage protocol applied during measurements. Values represent means ± SEM, n = 8 and 10, respectively.</p

Effect of ORM-10962 (0.3 mg/kg) on ventricular arrhythmias induced by reperfusion after 6 min coronary artery ligation in anesthetized (60 mg/kg <i>i</i>.<i>p</i>.) rats.

<p>Effect of ORM-10962 (0.3 mg/kg) on ventricular arrhythmias induced by reperfusion after 6 min coronary artery ligation in anesthetized (60 mg/kg <i>i</i>.<i>p</i>.) rats.</p

Lack of effect of ORM-10962 on the rapid and slow delayed rectifier outward potassium currents (I_Kr and I_Ks) in dog ventricular myocytes.

<p><b>Panels A and B.</b> Original I_Kr (top) and I_Ks (bottom) current traces (left panels) recorded under control conditions and in the presence of 1 μM ORM-10962, and the corresponding I-V current-voltage relationships (right panels) before and after application of 1 μM ORM-10962, respectively. The insets in the I-V diagrams show the voltage protocol applied during measurements. Values represent means ± SEM, n = 6 and 6, respectively.</p

Suspension of ouabain induced arrhythmias by ORM-10962, administered after the termination of ouabain infusion (10 μg/kg/min for 16 min) in anesthetized guinea pigs.

<p>Suspension of ouabain induced arrhythmias by ORM-10962, administered after the termination of ouabain infusion (10 μg/kg/min for 16 min) in anesthetized guinea pigs.</p

The Effect of a Novel Highly Selective Inhibitor of the Sodium/Calcium Exchanger (NCX) on Cardiac Arrhythmias in <i>In Vitro</i> and <i>In Vivo</i> Experiments - Fig 5

<p><b>Panel A</b>. Lack of effect of ORM-10962 on I_NaL current in dog ventricular myocytes. Original current traces show that 1 μM ORM-10962 does not influence I_NaL, while 20 μM TTX blocks the current. The applied voltage protocol is illustrated on the top of the Figure. <b>Panel B.</b> Lack of effect of 1 μM ORM-10962 on peak I_Na measured in Nav1.5 expressed chinese hamster ovary (CHO) cells. The ORM-10962 did not influence the current (red line and bar), while 20μM TTX significantly reduced the current (blue line and bar). The applied voltage protocol is illustrated on the top of the Figure. <b>Panel C.</b> Lack of effect of ORM-10962 on Na⁺/K⁺ pump current. <i>Top trace</i> shows that 1 μM ORM-10962 does not influence I_p, however, a slight gradual decrease of the current was detected. An original current record in the <i>middle trace</i> indicates that the slight gradual current decrease, similar to that shown in the <i>top trace</i>, was also observed without addition of ORM-10962. <i>Bottom trace</i>: Strophanthin (10 μM) completely blocks Na⁺/K⁺ pump current. I_p was defined as the difference between currents measured in 5 mM K⁺ and in 0 mM K⁺ containing solutions. The current traces were recorded at a steady potential of -30 mV.</p