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Simultaneous measurement of intracellular calcium and ventricular function in the phospholamban-deficient mouse heart
T G Hampton1, E G Kranias, J P Morgan
1Charles A. Dana Research Institute, Department of Medicine, Beth Israel Hospital, Boston, Massachusetts, USA.
Insights
Phospholamban deficiency in mice leads to higher intracellular calcium (Cai2+) levels and faster calcium handling. This results in increased heart contractility and quicker relaxation, highlighting phospholamban's regulatory role.
Area of Science:
- Cardiology
- Molecular Biology
- Physiology
Background:
- Phospholamban is a key regulator of cardiac sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity.
- Understanding phospholamban's role in intact hearts is crucial for cardiac function research.
Purpose of the Study:
- To measure intracellular calcium (Cai2+) alongside cardiac function in intact mouse hearts.
- To investigate the functional consequences of phospholamban deficiency in the mouse heart.
Main Methods:
- Retrograde perfusion of isolated mouse hearts with Krebs-Henseleit solution.
- Aequorin injection for intracellular calcium transient measurement.
- Left ventricular pressure monitoring using a balloon catheter.
Main Results:
- Phospholamban-deficient mouse hearts exhibited significantly higher peak intracellular calcium (Cai2+) compared to wild-type.
- Calcium exchange was markedly faster in phospholamban-deficient hearts.
- Increased Cai2+ transient amplitude and decreased duration correlated with enhanced contractility and faster relaxation.
Conclusions:
- This study presents the first recordings of intracellular calcium transients in intact mouse hearts.
- Direct evidence demonstrates phospholamban as a critical regulator of basal intracellular calcium (Cai2+) and cardiac contractility.
Abstract:
We describe the procedure for the measurement of intracellular calcium (Cai2+) simultaneously with function in the intact mouse heart and report findings in phospholamban-deficient mice. Seven phospholamban-deficient and six age-matched wild-type hearts were perfused retrogradely with oxygenated Krebs-Henseleit solution. Aequorin was injected into the apex of five hearts from each group to characterize Cai2+ transients. A pressure-sensing balloon was positioned in the left ventricle. Peak Cai2+ was significantly greater in the phospholamban-deficient hearts than in wild-type hearts (0.98 +/- 0.07 vs. 0.78 +/- 0.09 microM, p < 0.05). Calcium exchange was significantly faster in the phospholamban-deficient hearts. Cai2+ transients of significantly increased amplitude and decreased duration in phospholamban-deficient hearts correlated with increased contractility and faster relaxation. We report the first recordings of intracellular calcium transients in the intact heating mouse heart and present direct evidence that phospholamban is a key regulator of basal Cai2+ and contractility.