Relationship between myocardial β-adrenergic receptor characteristics and the incidence of ascites in broiler chickens

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Abstract
The present study was carried out to determine, first, the cardiac β -adrenergic receptor characteristics of normal chickens and chickens with heart failure and, second, the characteristics of myocardial β -adrenergic receptors in non-hypertrophied hearts in broilers exposed to two different altitude and temperature programmes. The density of β -adrenergic receptors was significantly lower in myocardial cells in right ventricular failure birds compared with healthy birds. The binding capacity of β -adrenergic receptors was reduced in the non-hypertrophied ventricles after exposure to high altitude in the younger but not in older chickens. At both altitudes, β -adrenergic receptor binding capacity was not significantly different in low temperature compared with normal temperature birds. These data support the hypothesis of β -adrenergic receptor downregulation as one of the mechanisms of cardiac cell adaptation to hypertrophy or hypoxia. Second, the acclimatization to high altitude in older chickens resulted in a normalization of β -receptor capacity in those broilers that were not affected by right ventricular failure and ascites.