Age-dependent changes in expression of alpha 1-adrenergic receptors in rat myocardium.

The expression of alpha 1-adrenergic receptors within ventricular myocardium of rats ranging in age from 21 days of fetal life to 24 months after birth was measured from [125I] 2-(beta hydroxy phenyl) ethylaminomethyl tetralone binding isotherms. No difference was observed in binding affinity between any of the age groups studied. The number of alpha 1-adrenergic receptors was found to be 60-120% higher in membranes from fetal or immature rats up to 25 days of age when compared with adult animals. The increased expression of alpha 1-adrenergic receptors in the developing heart relative to that observed in adult heart is consistent with the hypothesis that alpha 1-adrenergic receptor stimulation may modulate protein synthesis and growth in mammalian myocardium.