Related Experiment Videos
Class III antiarrhythmic effects of ceruloplasmin on rat heart
R Atanasiu1, L Gouin, M A Mateescu
1Department of Physiology, Université de Montréal, Canada.
Insights
Ceruloplasmin, a protein, was found to prolong cardiac refractory periods and action potentials in rats, suggesting it has Class III antiarrhythmic effects. This effect was observed even when the protein was denatured, indicating a specific action.
Area of Science:
- Cardiovascular Physiology
- Electrophysiology
- Pharmacology
Background:
- Ceruloplasmin demonstrates protective effects against reperfusion-induced arrhythmias in isolated rat hearts.
- The protective action of ceruloplasmin is lost upon heat denaturation.
- The specific electrophysiological mechanisms underlying ceruloplasmin's antiarrhythmic effects require elucidation.
Purpose of the Study:
- To investigate whether ceruloplasmin alters key electrophysiological properties in the heart.
- To assess changes in ventricular effective refractory periods and action potential duration.
- To determine the specificity of ceruloplasmin's electrophysiological effects by comparing it with denatured ceruloplasmin and other substances.
Main Methods:
- Isolated rat hearts and ventricular preparations were used.
- Measurements included ventricular effective refractory periods, conduction time, and action potential duration (APD50, APD75, APD90).
- Effects of native and heat-denatured ceruloplasmin, superoxide dismutase, catalase, deferoxamine, and albumin were evaluated at various concentrations.
Main Results:
- Ceruloplasmin significantly increased effective refractory period in a concentration-dependent manner (26-89%) and prolonged action potential duration (APD50: 52%, APD75: 64%, APD90: 41%).
- Heat-denatured ceruloplasmin also increased effective refractory period (33-70%) but did not significantly alter conduction time.
- Superoxide dismutase, catalase, deferoxamine, and albumin showed no significant effects on effective refractory period or conduction time, suggesting specificity for ceruloplasmin.
Conclusions:
- Both native and heat-denatured ceruloplasmin prolong effective refractory period and action potential duration, indicating potential Class III antiarrhythmic effects.
- The observed electrophysiological effects of ceruloplasmin appear specific and distinct from antioxidant or albumin effects.
- While ceruloplasmin exhibits Class III-like properties, these may not fully explain its antifibrillatory action during cardiac reperfusion.
Abstract:
Recently it has been shown that ceruloplasmin presents a protective action against reperfusion-induced arrhythmias in the isolated perfused rat heart, an effect that is lost when the protein is denaturated by heat. The present study was carried out to see whether ceruloplasmin can alter electrophysiological properties such as ventricular effective refractory periods, conduction time, and action potential duration calculated at 50, 75, and 90% levels of repolarization (APD50, APD75, APD90). To check the specificity of the electrophysiological effects of ceruloplasmin, we have also compared them with those of heat-denatured ceruloplasmin, superoxide dismutase, catalase, deferoxamine, and albumin. In isolated rat hearts, ceruloplasmin (0.25-3 microM) (n = 8 for each concentration) was shown to increase the effective refractory period in a concentration-dependent manner by 26 to 89%. Conduction time was not significantly altered. Heat-denatured ceruloplasmin (0.50-3 microM) (n = 8 for each concentration) increased the effective refractory period by 33 to 70% and did not affect the conduction time. In contrast, superoxide dismutase (1-4 microM), catalase (1-2 microM), deferoxamine (500 microM-1 mM), and albumin (1-4 microM) (n = 8 for each substance and for each concentration) had no significant effect on effective refractory period and conduction time at any dose, suggesting that the ceruloplasmin effect might be specific. In rat ventricular preparations, ceruloplasmin (1 microM) also induced a constant prolongation of APD50 (52%), APD75 (64%), and APD90 (41%) after 15 min of infusion (n = 6). The prolongation of effective refractory period and of action potential duration, by native and heat-denatured ceruloplasmin, suggests that this substance has specific class III effects, although this cannot entirely account for its antifibrillatory action at reperfusion in isolated rat hearts.