Related Experiment Videos
Quinidine enhances intracellular Ca2+ accumulation during rapid stimulation
J Hasegawa1, M Tsuboi, K Narasaki
1Department of Internal Medicine, Faculty of Medicine, Tottori University, Yonago, Japan.
General Pharmacology
|September 1, 1995
Summary
Quinidine alters intracellular calcium (Ca2+) levels in guinea-pig heart muscle by slowing its removal and reducing peak levels. This modulation of Ca2+ dynamics may explain quinidine's complex effects on heart rhythm.
Area of Science:
- Cardiology
- Pharmacology
- Cell Physiology
Background:
- Quinidine is an antiarrhythmic drug with known effects on cardiac electrophysiology.
- Intracellular calcium (Ca2+) handling is critical for myocardial contractility and rhythm regulation.
Purpose of the Study:
- To investigate the specific effects of quinidine on intracellular Ca2+ concentration ([Ca2+]i) dynamics in guinea-pig myocardium.
- To elucidate the mechanisms by which quinidine modulates [Ca2+]i during cardiac stimulation.
Main Methods:
- Fura-2 fluorescence imaging was used to measure [Ca2+]i in isolated guinea-pig cardiac preparations.
- Measurements were conducted under varying stimulation frequencies and quinidine concentrations.
- Analysis of diastolic Ca2+ decay kinetics and systolic/diastolic [Ca2+]i levels.
Main Results:
- Quinidine reduced systolic [Ca2+]i and increased end-diastolic [Ca2+]i during stimulation.
- Quinidine significantly prolonged the rapid decay phase of diastolic [Ca2+]i, particularly at higher concentrations (20-60 microM).
- The rate of slow recovery from [Ca2+]i accumulation was not affected by quinidine.
Conclusions:
- Quinidine modulates cardiac [Ca2+]i by balancing a slower decay rate with reduced systolic levels.
- These alterations in [Ca2+]i handling by quinidine may underlie its dual anti-arrhythmic and pro-arrhythmic properties.
- Understanding these mechanisms is crucial for predicting quinidine's clinical effects in cardiac conditions.