Journal: Frontiers in Endocrinology

Article Title: Cisapride induced hypoglycemia via the KCNH6 potassium channel

doi: 10.3389/fendo.2022.1011238

Figure Lengend Snippet: Cisapride inhibited HERG channels in transfected HEK293 cells HERG currents were recorded in transfected HEK293 cells. Cells were voltage-clamped at −80 mV for 1 s, depolarized from −60 mV to +50 mV for 3 s and repolarized to −40 mV for 3 s under stimulation with (A) E4031, dofetilide or (B) cisapride. (C) The time-dependent step current and (D) peak tail current I-V curves were recorded before and after cell perfusion with 1 𝜇mol/L cisapride. (E) Cells were depolarized to a voltage of +20 mV for 3 s using a stepped procedure. Peak tail currents were recorded at different cisapride concentrations (10 and 100 nmol/L). (F) The IC50 of cisapride was calculated. The concentration−response curve was fitted to a Hill equation. n=4 for each group (A–F) . ** P < 0.01, *** P < 0.005 vs. Ctrl.

Article Snippet: E4031 and dofetilide were purchased from MedChemExpress.

Techniques: Transfection, Concentration Assay

Journal: Biomedicines

Article Title: Acetylcholine Reduces I Kr and Prolongs Action Potentials in Human Ventricular Cardiomyocytes

doi: 10.3390/biomedicines10020244

Figure Lengend Snippet: Functional effects of the ACh-induced reduction in I Kr on a model human ventricular cardiomyocyte (O’Hara–Rudy human ventricular cell ). ( a ) APs (top) and associated I Kr (bottom) at a stimulus frequency of 1 Hz. ( b ) APs (top) and associated I Kr (bottom) at a stimulus frequency of 3 Hz. ( c ) AP duration at 50% and 90% repolarization (APD 50 and APD 90 , respectively) at stimulus frequencies ranging from 0.5 to 3.0 Hz. ( d ) Human left ventricular myocardial slice: superimposed recording of APs during control and after superfusion with dofetilide (50 nM) at a BCL of 1000 ms.

Article Snippet: Dofetilide was purchased from Carbosynth Ltd., Compton, UK.

Techniques: Functional Assay, Control

Journal: EMBO Molecular Medicine

Article Title: A new hERG allosteric modulator rescues genetic and drug‐induced long‐ QT syndrome phenotypes in cardiomyocytes from isogenic pairs of patient induced pluripotent stem cells

doi: 10.15252/emmm.201606260

Figure Lengend Snippet: Chemical structures of LUF7243, LUF7244, LUF7344, LUF7346 and LUF7389. Percentage of specific binding of [ 3 H]dofetilide to the hERG channel after 6 min of dissociation induced by 10 μM dofetilide in the absence (control) or presence of 10 and 50 μM of LUF compounds. The specific binding of [ 3 H]dofetilide in the absence of test compounds was set as B control , while the specific binding in their presence was set as B . * P < 0.05 versus control; N = 3–4. Representative traces of hERG activation (left), inactivation (middle) and deactivation (right) measured in HEK293 hERG cells under baseline conditions (black) and in the presence of 3 μM LUF7346 (red). Insets: voltage‐clamp protocols. Steady‐state activation (empty symbols) and inactivation (filled symbols) curves for I Kr under baseline conditions (black) and in the presence of 3 μM LUF7346 (red). The corresponding Boltzmann's fittings are superimposed to data points. * P < 0.05 versus baseline. N = 11–14. Plot of the time constants (τ) of deactivation derived from biexponential fittings under baseline conditions (black) and in the presence of 3 μM LUF7346 (red). * P < 0.05 versus respective baseline. N = 8. Data information: (B) Two‐tailed unpaired t ‐test. P < 0.0001 for all tested LUF compounds compared to the control group at both 10 and 50 μM. (D) Repeated‐measures two‐way ANOVA with Sidak's multiple comparisons test. Adjusted P ‐values for inactivation: −100 mV: > 0.9999; −90 mV: > 0.9999; −80 mV: 0.3922; −70 mV: 0.9636; −60 mV: 0.0006; −50 mV: < 0.0001; −40 mV: < 0.0001; −30 mV: < 0.0001; −20 mV: < 0.0001; −10 mV: < 0.0001; −10 mV: 0.0011; 0 mV: 0.0111; 10 mV: 0.0343; 20 mV: 0.4871; 30 mV: > 0.9999. Adjusted P ‐values for activation: −60 mV: > 0.9999; −50 mV: 0.9998; −40 mV: > 0.9999; −30 mV: 0.8854; −20 mV: 0.2129; −10 mV: 0.1188; 0 mV: 0.9944; 10 mV: > 0.9999; 20 mV: 0.8340; 30 mV: 0.9841. (E) Paired two‐way ANOVA with Sidak's multiple comparisons test. Adjusted P ‐values for deactivation τ fast : −120 mV: 0.01, −100 mV: < 0.0001, −80 mV: < 0.0001. Adjusted P ‐values for deactivation τ slow: −120 mV: 0.01, −100 mV: < 0.0001, −80 mV: < 0.0001. (B, D, E) Data are expressed and plotted as the mean ± SEM.

Article Snippet: Tritium‐labelled dofetilide (specific activity: 82.3 Ci/mmol) was obtained from PerkinElmer (MA, USA).

Techniques: Binding Assay, Control, Activation Assay, Derivative Assay, Two Tailed Test

Journal: The Journal of General Physiology

Article Title: Facilitation of I Kr current by some hERG channel blockers suppresses early afterdepolarizations

doi: 10.1085/jgp.201812192

Figure Lengend Snippet: Rabbit cardiac myocyte APs are more stable in nifekalant than dofetilide. AP responses in the isolated rabbit ventricular myocytes were stimulated by minimal current injection at 0.5 Hz in whole-cell current clamp mode at 37°C. (A and B) After recording of the control responses (black lines), cells were treated with either 1 µM dofetilide (pink lines) or 10 µM nifekalant (green line). (A) Representative AP responses without (left) or with (right) EAD in 1 µM dofetilide. Of 19 cells treated with 1 µM dofetilide, five cells showed EAD responses (26%). 14 cells showed the prolongation of APD in 1 µM dofetilide but did not show EAD responses. (B) Representative AP responses in 10 µM nifekalant. All cells treated with 10 µM nifekalant showed prolongation of APD upon 1 µM dofetilide but did not show EAD responses. (C and D) Prolongation of APD and beat-to-beat instability by 1 µM dofetilide and 10 µM nifekalant. Only the data from the cells showing AP responses without EAD were included in this analysis (14 cells of 1 µM dofetilide-treated group; 19 cells of 10 µM nifekalant-treated group). 30 consecutive APs responses in control and under the treatment of either 1 µM dofetilide or 10 µM nifekalant were recorded, and APD 90 of the i +1th action potential (APD 90 i+1) was plotted against APD 90 of the one action potential before ( i th; APD 90 i). APD 90 s were prolonged by treatment with 1 µM dofetilide (C) or 10 µM nifekalant (D) compared with control. 1 µM dofetilide prolonged APD 90 longer (P = 4.26 × 10 −13 , Student’s t test) than 10 µM nifekalant. The control APD 90 s were identical between dofetilide- and nifekalant-treated cells (P = 0.58).

Article Snippet: Dofetilide was obtained from Alomone Labs. For comparisons of dofetilide and nifekalant effects on APs in ventricular myocyte, stock solutions were prepared, and then the researcher was blinded to their identity during experiments and analysis.

Techniques: Isolation, Injection