agonist-induced internalization was very rapid , in the order of few minutes . beta adrenergic receptor internalization was very specific : the alpha adrenergic agonist phenylefrine had almost no effect on beta receptor levels , while isoproterenol treatment had no effect on the number of alpha adrenergic or nicotinic receptors expressed at the cell surface of these cells . beta adrenergic receptor internalization is probably the major mechanism responsible for catecholamine desensitization in smooth muscle cells .
C0022245
isoproterenol
C0007412
catecholamine