Parallel stimulation of ACTH, beta-LPH + beta-endorphin and alpha-MSH release by alpha-adrenergic agents in rat anterior pituitary cells in culture.
Characteristics of the alpha-adrenergic stimulation of ACTH, beta-endorphin + beta-LPH and alpha-MSH release were studied in rat anterior pituitary cells in primary culture. Parallel changes of ACTH, beta-endorphin + beta-LPH and alpha-MSh release were found under all stimulatory and inhibitory conditions by natural and synthetic catecholamine agonists and antagonists. (-)Epinephrine and (-)norepinephrine lead to a 8--10-fold stimulation of peptide release at ED50 values of 20 and 90 nM, respectively. The stereoselectivity of the alpha-adrenergic stimulatory action on peptide release is indicated by a 100-fold higher activity of (-)- than (+)norepinephrine while (-)epinephrine is 10 times more potent than the corresponding (+) stereoisomer. The involvement of a typical alpha-adrenergic mechanism in the control of release of ACTH, beta-endorphin and related peptides in rat anterior pituitary gland is indicated by the following order of potency of a series of catecholaminergic agents (ED50 values): (-)epinephrine (20 nM) greater than (-)norepinephrine (90 nm) greater than phenylephrine (400 nM) greater than isoproterenol (6000 nM). The stimulatory effect of (-)epinephrine or phenylephrine is completely reversed by low concentrations of the alpha-adrenergic antagonist phentolamine while the beta-adrenergic antagonist propranolol has no effect up to 10 muM. Beside providing an easily accessible pure population of post-synaptic alpha-adrenergic receptors having potential applications as a model for other less accessible alpha-adrenergic brain systems, the present data suggest the possibility of the direct involvement of a catecholamine in the physiological control of ACTH secretion in the rat anterior pituitary gland.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology; D004723:Endorphins / Q000378:metabolism*; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D001615:beta-Endorphin; D008083:beta-Lipotropin / Q000378:metabolism*
D000316:Adrenergic alpha-Agonists; D004723:Endorphins; D010656:Phenylephrine; D012701:Serotonin; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones; D008083:beta-Lipotropin; D007545:Isoproterenol; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine