Related Experiment Videos
Calcium current in congestive heart failure of hamster cardiomyopathy
1Department of Physiology, New York College of Osteopathic Medicine, Old Westbury 11568.
Insights
Cardiomyopathic hamsters show reduced L-type calcium current (ICa) in heart cells, potentially explaining their weakened contractions. This study highlights ion channel dysfunction in heart failure.
Area of Science:
- Cardiovascular Physiology
- Molecular Cardiology
- Heart Failure Research
Background:
- Congestive heart failure is characterized by impaired cardiac function.
- Ventricular cardiomyocytes play a crucial role in heart contractility.
- Ion channel function is vital for maintaining normal electrical activity in the heart.
Purpose of the Study:
- To investigate L-type calcium current (ICa) in cardiomyocytes of cardiomyopathic hamsters.
- To compare ICa characteristics between diseased and normal hamsters.
- To elucidate the role of ICa dysfunction in the pathophysiology of heart failure.
Main Methods:
- Whole-cell patch-clamp electrophysiology was used to measure ICa.
- Experiments were conducted on ventricular cardiomyocytes from aged cardiomyopathic (CM) and normal (N) Syrian hamsters.
- Voltage-clamp protocols were applied to assess ICa amplitude, conductance, and kinetics.
Main Results:
- L-type calcium current (ICa) amplitude was significantly lower in CM hamsters compared to N hamsters.
- Maximum specific conductance of ICa was significantly greater in N than in CM hamsters.
- Time constants for inactivation and recovery from inactivation were significantly longer in CM hamsters.
Conclusions:
- Reduced ICa amplitude in cardiomyopathic hamsters may stem from decreased conductance or density of L-type calcium channels.
- This ICa dysfunction likely contributes to the depressed cardiac contractions observed in this heart failure model.
- Findings provide insights into the molecular mechanisms underlying heart failure progression.
Abstract:
L-type calcium current (ICa) was examined using the whole cell patch-clamp method in ventricular cardiomyocytes of 400- to 458-day-old cardiomyopathic (CM) Syrian hamsters (BIO 14.6 strain) that exhibited pathology consistent with congestive heart failure. Controls were comparably aged normal (N) hamsters (BIO F1B strain). At -35-mV holding potential, ICa, normalized to picofarads of membrane capacitance, was significantly lower in amplitude in cells of CM vs. N at 300-ms duration voltage command steps of -25 to +25 mV (10-mV increments from -25 to +65 mV). Estimates of reversal potential for ICa were similar between strains, whereas average maximum specific conductance was significantly greater for N than for CM. Inactivation time constants (biexponential) and the time constant for recovery from inactivation were significantly longer for CM vs. N. Steady-state activation and inactivation data were similar between strains by Boltzmann fit. Results suggest that ICa amplitude is below normal in CM, possibly due to decreased conductance or density of functional L-type channels. This may contribute to the depressed contractions in this model of congestive heart failure.