Postnatal beta-adrenergic receptor [(3H] CGP-12177) binding in myocardial slices of cardiomyopathic hamsters.

A muscle slice technique was used to compare the development changes in binding of the beta-adrenergic antagonist, [3H]CGP-12177 (CGP), in right ventricles of male Canadian Hybrid Farms CHF 147 cardiomyopathic hamsters and two strains of control healthy animals, golden Syrian (GH) and CHF 148 albino noncardiomyopathic (AH) hamsters. CGP binding to myocardial slices was saturable, reversible, stereospecific, proportional to slice number and of high affinity. Bmax in GH and AH myocardium was not altered with age although there was a tendency to decrease between 16 and 30 days of age in both strains. In the cardiomyopathic ventricles, receptor number decreased between 30 (7.07 +/- 0.74 fmol/mg wet weight) and 60 days of age (4.58 +/- 0.52) (P less than 0.05) and remained at the lower level thereafter. Bmax in cardiomyopathics was slightly higher than that of either GH (5.01 +/- 0.88) or AH (5.05 +/- 0.82) at 30 days of age (P less than 0.05) but was not different at the other ages tested. Kd was decreased in GH at 30 days of age but was unaltered during postnatal development in either the AH or cardiomyopathic hearts. The elevated level of cell surface beta-adrenergic receptors in the cardiomyopathic ventricle at a time when necrotic lesions are developing may be important with respect to the pathogenesis of cardiomyopathy in these animals.