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

The present study was carried out to determine, first, the cardiac beta -ad renergic receptor characteristics of normal chickens and chickens with hear t failure and, second, the characteristics of myocardial beta -adrenergic r eceptors in non-hypertrophied hearts in broilers exposed to two different a ltitude and temperature programmes. The density of beta -adrenergic recepto rs was significantly lower in myocardial cells in right ventricular failure birds compared with healthy birds. The binding capacity of beta -adrenergi c receptors was reduced in the non-hypertrophied ventricles after exposure to high altitude in the younger but not in older chickens. At both altitude s, beta -adrenergic receptor binding capacity was not significantly differe nt in low temperature compared with normal temperature birds. These data su pport the hypothesis of beta -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 norm alization of beta -receptor capacity in those broilers that were not affect ed by right ventricular failure and ascites.