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Purpose : We designed this study to investigate the mechanism of reduced cardiac β-adrenoceptor function that is associated with aging.Materials and Methods : We assessed the density and affinity of β-adrenoceptors by (-) - 125I iodocyanopindolol binding in the right atrial appendages obtained from 40 patients of varying age (range : 2 to 56 years) undergoing open-heart surgery. The mean right atrial pressure and cardiothoracic ratio were measured in all of the patients.Results : There was a significant negative correlation between human right atrial β-adrenoceptor density and patient age (r = 0.575, p <0.001). Neither preoperative mean right atrial pressure nor preoperative cardiothoracic ratio was correlated with β-adrenoceptor density. The affinity of β-adrenoceptors did not correlate with patient age.Conclusions : The decrease in human cardiac β-adrenoceptor function associated with increasing age is due, in part, to the reduced cardiac β-adrenoceptor density.
Tsuda et al. (1998) studied this question.