Inhibition of hypothalamic somatostatin release by beta-adrenergic antagonists.
A number of in vivo studies suggest that hypothalamic somatostatin (SRIF) tone is stimulated by the beta-adrenergic system. Employing dispersed adult male rat hypothalamic cells, we studied the effects of beta-adrenergic antagonists on the release of hypothalamic SRIF. Propranolol, at concentrations of 1-100 microM, had no detectable effect on basal SRIF release, but caused dose-dependent inhibition of SRIF release stimulated by ouabain. Two other beta-adrenergic antagonists, labetolol and metoprolol, also caused inhibition of ouabain-stimulated SRIF release. The alpha 2-agonist clonidine was without effect on SRIF release under basal or stimulated conditions. GH secretion from monolayers of dispersed rat anterior pituitary cells was also examined. Propranolol (1-100 microM) had no significant effect on basal GH secretion or GH secretion stimulated by rat GRF. In conclusion, 1) beta-adrenergic antagonists caused inhibition of stimulated SRIF release; 2) clonidine had no detectable effect on SRIF release; and 3) propranolol did not affect GH secretion in vitro. These findings support the hypothesis that beta-adrenergic antagonists augment GH responsivity by inhibiting hypothalamic SRIF release.
Richardson
S B
SB
Research Program, Veterans Administration, Medical Center, New York, New York 10010.
Twente
S
S
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D003000:Clonidine / Q000494:pharmacology; D013006:Growth Hormone / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007741:Labetalol / Q000494:pharmacology; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000378:metabolism*
D000319:Adrenergic beta-Antagonists; D013004:Somatostatin; D010042:Ouabain; D013006:Growth Hormone; D011433:Propranolol; D008790:Metoprolol; D003000:Clonidine; D007741:Labetalol