Key result
Ouabain exposure similarly increased contractile force in neonatal and adult canine ventricular muscle, but adult preparations developed more delayed afterdepolarizations.
Why the study?
Does ouabain exposure alter electromechanical properties differently in neonatal versus adult canine ventricular muscle?
Does ouabain exposure alter electromechanical properties differently in neonatal versus adult canine ventricular muscle?
The higher glycoside tolerance in neonatal dogs compared to adults may be due to differences in mechanisms developing abnormal ventricular automaticity rather than requiring higher levels for contractility augmentation.
Highlights potential developmental differences in glycoside arrhythmogenicity in canine models; leaves open translation to human neonatal tolerance or dosing.
In this report, alterations between the electrical and mechanical responses of isolated neonatal and adult canine ventricular muscle preparations before and after ouabain exposure are described. No significant differences were observed between the two age groups in the concentration-dependent effects of ouabain on increasing contractile force or decreasing maximum diastolic transmembrane potential. The action potential plateau duration was decreased by high concentrations of ouabain (0.3-1 microM) in both neonatal and adult ventricular muscle. In addition, more adult preparations developed delayed afterdepolarizations associated with aftercontractions after exposure to ouabain than did neonatal preparations. These results suggest that the higher glycoside tolerance in neonatal dogs as compared with adults may be due in part to differences in the mechanisms responsible for development of abnormal ventricular automaticity. The results may also indicate that immature animals do not require higher glycoside levels to produce augmentation of cardiac contractility.
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Lathrop et al. (1989) studied this question. Ouabain vs. Before ouabain exposure / between age groups was evaluated on Electromechanical responses (contractile force, maximum diastolic transmembrane potential, action potential plateau duration, delayed afterdepolarizations). Ouabain exposure similarly increased contractile force in neonatal and adult canine ventricular muscle, but adult preparations developed more delayed afterdepolarizations.
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