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Effects of different inotropic interventions on myocardial function in the developing rabbit heart
Holger Schiffmann1, Markus Flesch, Claudia Häuseler
1Department of Pediatrics, University of Göttingen, Germany. schiffi@med.uni-goettingen.de
Basic Research in Cardiology
|May 10, 2002
Summary
Neonatal rabbit hearts show developing contractility and relaxation, with improved function linked to lower Na(+)-Ca2+ exchanger expression. Adult hearts exhibit enhanced responses to inotropic agents compared to neonatal ones.
Area of Science:
- Cardiovascular Physiology
- Developmental Biology
- Molecular Cardiology
Background:
- Mammalian heart development involves significant changes in myocardial performance.
- Understanding these functional ontogenetic shifts is crucial for pediatric cardiology.
- The roles of specific proteins like the Na(+)-Ca2+ exchanger in this process require elucidation.
Purpose of the Study:
- To investigate the ontogeny of myocardial function in developing rabbit hearts.
- To assess the impact of various inotropic interventions on cardiac performance across different developmental stages.
- To correlate myocardial function with the protein expression of the sarcolemmal Na(+)-Ca2+ exchanger and sarcoplasmic Ca(2+)-ATPase.
Main Methods:
- Utilized isolated, antegrade-perfused rabbit hearts at various developmental stages (2, 8, 14, 28 days).
- Measured myocardial function, including maximal developed pressure velocity (dP/dtmax) and peak negative pressure velocity (dP/dtmin).
- Administered inotropic agents (isoproterenol, ouabain, calcium, BDF 9148) and analyzed protein expression levels.
Main Results:
- Neonatal hearts showed age-dependent increases in dP/dtmax and dP/dtmin from day 2 to 8.
- Inotropic agents increased dP/dtmax and dP/dtmin concentration-dependently, with significant differences between age groups for some agents.
- Adult hearts exhibited significantly higher increases in dP/dtmax and dP/dtmin with isoproterenol compared to neonatal hearts.
- Declining Na(+)-Ca2+ exchanger protein expression from neonatal to adult hearts correlated with increased myocardial function.
Conclusions:
- Neonatal cardiac contractility and relaxation are generally lower than in adult hearts.
- Decreased Na(+)-Ca2+ exchanger expression is associated with improved myocardial contractility and relaxation during heart development.
- The developmental trajectory of myocardial function is influenced by age-related changes in protein expression and responsiveness to inotropic stimuli.