Journal of Neuroscience, Vol 3, 725-732, Copyright © 1983 by Society for Neuroscience
Activation of beta 2-adrenergic receptors on mouse anterior pituitary tumor cells increases cyclic adenosine 3':5'-monophosphate synthesis and adrenocorticotropin release
TD Reisine, S Heisler, VY Hook and J Axelrod
AtT-20 cells comprise a mouse anterior pituitary tumor cell line that
synthesizes and secretes adrenocorticotropin hormone (ACTH). beta-
Adrenergic receptors were characterized on AtT-20 cells using receptor
binding methodology and the ability of beta-receptor agonists to stimulate
intracellular cyclic adenosine 3':5'-monophosphate (cAMP) formation and the
release of ACTH immunoreactivity. The density of beta- receptors on
membrane preparations of these cells is 64 fmol/mg of protein and their
affinity constant (KD value) for tritiated dihydroalprenolol is 11 nM. The
binding of [3H] dihydroalprenolol to AtT-20 cells is stereoselectively
inhibited by propranolol and isoproterenol but is not affected by
phentolamine. The beta-receptors on these cells appear to be of the beta
2-receptor subtype since a selective beta 2-receptor agonist, salmefamol,
can inhibit [3H]dihydroalprenolol binding, whereas practolol, a beta
1-receptor blocker, is ineffective. (-)-Isoproterenol stimulates cAMP
formation in AtT-20 cells and this effect is blocked by dl-propranolol.
Both l- epinephrine and l-norepinephrine induce dose-dependent increases in
cAMP formation with the former agonist being more potent. Salmefamol also
stimulates cAMP formation in these cells. The secretion of ACTH from AtT-20
cells is induced by (-)-isoproterenol as well as by other adrenergic
agonists. The isoproterenol effect on ACTH release is stereoselective,
calcium dependent, and blocked by dl-propranolol but not by phentolamine or
practolol.