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Postnatal changes in contractile time parameters, calcium regulatory proteins, and phosphatases
I Gombosova1, P Boknik, U Kirchhefer
1Institut fur Pharmakologie und Toxikologie, Westfalische Wilhelms-Universitat, D-48149 Munster, Germany.
The American Journal of Physiology
|June 25, 1998
Summary
Adult rat hearts exhibit faster contraction and relaxation than neonatal ones. This is linked to increased sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) expression and enhanced phospholamban phosphorylation due to reduced phosphatase activity.
Area of Science:
- Cardiovascular Physiology
- Molecular Cardiology
- Cardiac Muscle Contraction
Background:
- Neonatal and adult cardiac ventricular preparations exhibit distinct contractile properties.
- Understanding age-related differences in cardiac function is crucial for identifying mechanisms of cardiac maturation and disease.
Purpose of the Study:
- To investigate the molecular mechanisms underlying the faster contraction and relaxation times observed in adult rat ventricular preparations compared to neonatal ones.
- To determine the roles of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) and phospholamban in age-dependent changes in cardiac contractility.
Main Methods:
- Comparison of contractile parameters (time of contraction, time to peak tension, time of relaxation) between adult and neonatal rat ventricular preparations.
- Quantification of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) and phospholamban expression at both protein and mRNA levels.
- Measurement of Ca2+ uptake kinetics.
- Assessment of phospholamban phosphorylation status and phosphatase activity (Protein Phosphatase types 1 and 2A).
Main Results:
- Adult ventricular preparations showed significantly shorter contraction and relaxation times (approx. 50%) compared to neonatal preparations.
- SERCA expression (protein and mRNA) was significantly increased in adult vs. neonatal preparations, correlating with enhanced Ca2+ uptake (180%).
- Phospholamban levels were unchanged, but its phosphorylation was enhanced in adult hearts, associated with reduced phosphatase activity and protein levels.
Conclusions:
- Elevated sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) expression is a primary driver for the shortened contraction parameters in the adult rat heart.
- Increased phospholamban phosphorylation, resulting from diminished phosphatase activity, likely contributes to the enhanced cardiac function in adult rats.