Ontogeny of myocardial adrenoceptors II. Alpha adrenoceptors.

The maturation of myocardial alpha adrenoceptors was investigated in dogs. Alpha adrenoceptors were characterized by radioligand binding using [3H]-WB4101. In neonatal cardiac membranes, the binding of the ligand was rapid, reversible, of high affinity, saturable and stereoselective. The competition studies with adrenergic agonists and antagonists were indicative of alpha adrenoceptors. In adult dog cardiac membranes, consistent specific binding of the ligand could be demonstrated. These studies indicate that there is a decrease in alpha adrenergic receptor density of canine cardiac membranes during maturation.