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Updated: Feb 13, 2026
Isolation of High Quality Murine Atrial and Ventricular Myocytes for Simultaneous Measurements of Ca2+ Transients and L-Type Calcium Current
Published on: November 3, 2020
[Effects of isovitexin on transient outward potassium current of ventricular myocytes in rats]
Jing-Na Ren1, Ben-Long Rao1, Hong-Xin Ma1
1Department of Pharmaceutics, School of Medical Academy, Yangzhou University, Yangzhou 225001, China.
Abstract:
To investigate the effects of isovitexin Ⅳ on transient outward potassium current in rat ventricular myocytes. In this study, MTT assay was used to investigate the safe range of isovitexin. The results showed that the IC₅₀ of the drug was in the range of 10-30 μmol•L⁻¹, and the drug concentration of 1-3 μmol•L⁻¹ for the patch clamp test was within the safe range. In addition, the single ventricular myocytes were obtained by single-enzymatic hydrolysis through aortic retrograde perfusion. The transient outward potassium current (Ito) of rat ventricular myocytes was guided and measured by whole-cell patch-clamp technique and the changes of current characteristics were recorded after isovite was applied. When the concentration of IV was less than 0.1 μmol•L⁻¹, there was no significant effect on Ito. However, with the increase in the concentration of IV (≥0.3 μmol•L⁻¹), the peak of Ito was decreased gradually, from (32.32±2.9) pA/pF to （25.83±4.3） pA/pF, 1 μmol•L⁻¹ IV and (19.51±3.5) pA/pF, 3 μmol•L⁻¹ IV respectively, with an inhibition effect in a concentration-dependent manner. In the range of 1-3 μmol•L⁻¹, IV down-regulated the I-V curve of Ito significantly. The activation curve showed that IV can enable the maximum half activation potential (V1/2) to move to the positive direction, and the V1/2 was increased from (19.59±1.6) mV to (22.81±1.7) mV and (28.86±1.4) mV at concentration of 1, 3 μmol•L⁻¹, meanwhile the activation curve moved to the right. However, the maximum half inactivating potential (V1/2) of the steady-state inactivation curve of Ito was significantly decreased from (－51.43±0.99) mV to (－61.81±1.3) mV with concentration of 1 μmol•L⁻¹ and (－71.50±1.4) mV with concentration of 3 μmol•L⁻¹. The inactivation time constant of recovery from inactivation (τ) was up-regulated significantly from (94.89±0.73) ms to (118.5±1.5) ms and (162.4±1.4) ms at concentration of 1, 3 μmol•L⁻¹ respectively. Meanwhile IV could enable the inactivation recovery curve to move to the right, which suggested that it can prolong the recovery time from inactivation of the transient outward potassium channel. In conclusion, isovitexin had a high inhibitory effect on Ito in rat ventricular myocytes.
Insights
Isovitexin IV significantly inhibits transient outward potassium current (Ito) in rat ventricular myocytes in a concentration-dependent manner. This compound prolongs the recovery time of potassium channels from inactivation, suggesting potential therapeutic applications.
Area of Science:
- Cardiovascular Pharmacology
- Electrophysiology
- Molecular Biology
Background:
- Transient outward potassium current (Ito) plays a crucial role in cardiac action potential repolarization.
- Dysregulation of Ito is implicated in various cardiac arrhythmias.
- Isovitexin, a natural compound, has shown potential in modulating ion channel activity.
Purpose of the Study:
- To investigate the effects of Isovitexin IV on the transient outward potassium current (Ito) in rat ventricular myocytes.
- To determine the concentration-dependent inhibitory effects of Isovitexin IV on Ito.
- To elucidate the impact of Isovitexin IV on the gating properties of Ito.
Main Methods:
- MTT assay to determine the safe concentration range of Isovitexin IV.
- Isolation of single rat ventricular myocytes using enzymatic hydrolysis.
- Whole-cell patch-clamp technique to measure Ito and its characteristics.
- Analysis of current-voltage (I-V) relationships, activation, and inactivation curves.
Main Results:
- Isovitexin IV demonstrated a concentration-dependent inhibition of Ito, with significant effects observed at concentrations ≥0.3 μmol•L⁻¹.
- The compound reduced peak Ito current and significantly altered the I-V curve.
- Isovitexin IV shifted the activation curve positively and the inactivation curve negatively, prolonging the recovery time from inactivation.
Conclusions:
- Isovitexin IV exhibits a potent inhibitory effect on transient outward potassium current in rat ventricular myocytes.
- The observed effects suggest Isovitexin IV modulates potassium channel gating kinetics, specifically prolonging recovery from inactivation.
- These findings highlight Isovitexin IV as a potential candidate for further investigation in cardiac electrophysiology and arrhythmia management.
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