THE INFLUENCE OF AGE ON THE ALPHA-1-ADRENERGIC RECEPTORS IN RAT-LIVER PLASMA-MEMBRANES

Receptor density, equilibrium dissociation constant and receptor subtypes for alpha-1-adrenoceptors were studied in plasma membrane preparations from livers of newborn (2 to 4 days), mature (2 to 3 months) and senescent (24 to 26 months) rats. Receptor density increased significantly upon maturation and decreased slightly during post-maturational aging. Ligand affinity was unaffected by the age of the animal. Experiments with the alpha-1A-selective antagonists WB 4101 and phentolamine and with the irreversible alpha-1B-alkylating agent chloroethylclonidine suggest the presence of almost exclusively alpha-1B-adrenoceptors in the liver throughout the life span of the rat.