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[Inotropic effect of isoprenaline and noradrenaline on chick embryo heart]
L Ouedraogo1, L Sawadogo, R Tricoche
1Laboratoire de physiologie animale, faculté des sciences et techniques, université de Ouagadougou, Burkina Faso.
Insights
This study found that isoprenaline and noradrenaline stimulate beta-adrenergic receptors in developing chick hearts. Receptor activity and contractile protein maturity influence cardiac responses as the embryo develops.
Area of Science:
- Cardiology
- Developmental Biology
- Pharmacology
Context:
- The developing chick embryo heart provides a model for studying cardiac adrenergic receptor function.
- Understanding adrenergic receptor roles is crucial for developmental cardiology.
Purpose:
- To characterize the specific adrenergic receptors mediating positive inotropic responses in embryonic chick heart ventricles.
- To investigate age-dependent changes in adrenergic receptor efficacy and potency.
Summary:
- Isolated chick embryo ventricles were used to assess responses to isoprenaline and noradrenaline.
- Results indicated that both agonists act via beta-adrenergic receptors.
- Propranolol blocked the inotropic effects, while phentolamine did not, confirming beta-receptor involvement.
- Isoprenaline potency and overall efficacy increased with age, while noradrenaline potency decreased, likely due to uptake mechanisms.
Impact:
- This research clarifies the role of beta-adrenergic signaling in embryonic heart development.
- Findings suggest developmental changes in receptor density and contractile protein maturity influence cardiac contractility.
Abstract:
Isolated ventricles of developing chick embryo heart, paced at 1 Hz, were used to assess the positive inotropic responses to isoprenaline and noradrenaline in order to characterize the adrenergic receptors involved in these effects. In 7 day-old-chick embryo heart ventricle, isoprenaline and noradrenaline exhibited similar potencies and efficacies. Moreover, propranolol (1 microM) inhibited the positive inotropic effect of isoprenaline and noradrenaline, while pentholamine (3 microM) failed to affect the latter response; in addition, phenylephrine (1 microM-1 mM) had no positive inotropic effect. It was therefore concluded that isoprenaline and noradrenaline induce their effect via stimulation of beta-adrenergic receptors. The efficacy of isoprenaline and noradrenaline and the potency of isoprenaline increased from the 7th to 10th day while the potency of noradrenaline decreased. The decrease in noradrenaline potency with age was attributed to its uptake, while the increase in isoprenaline potency was attributed to the increase in beta-adrenergic receptors. However, the increase in efficacy of both isoprenaline and noradrenaline with age might be due to the higher density and/or higher maturity of contractile proteins.