title: Evidence for a growth hormone releasing factor mediating alpha-adrenergic influence on growth hormone secretion in the rat.
abstract: The effects of adrenergic receptor agonists on GH secretion were studied in adult, male rats pretreated with reserpine and somatostatin antiserum. Frequent blood samples were obtained from intra-aortic cannulae. Plasma GH was determined by radioimmunoassay. Reserpine (10 mg/kg i.p.) caused a complete suppression of the normal, pulsatile secretion of GH in all animals. Administration of somatostatin antiserum resulted in rapid elevations of plasma GH in reserpine-pretreated rats with peak levels at 30 min. GH levels then fell but remained slightly elevated for the duration of the sampling period (8 h). Apomorphine (0.5 mg/kg i.p.) had no effect on plasma GH levels, whereas clonidine (0.5 mg/kg i.p.) induced release of GH in both antiserum treated and control rats. The results indicate that the alpha-adrenergic influence on the secretion of GH is mediated not by inhibition of somatostatin release but rather by effects on the release of a GHRF.
mesh_terms: D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000502:physiology*; D007106:Immune Sera / Q000494:pharmacology; D008297:Male; D051381:Rats; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012110:Reserpine / Q000494:pharmacology; D013004:Somatostatin / Q000276:immunology
chemical_list: D007106:Immune Sera; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D013004:Somatostatin; D012110:Reserpine; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D003000:Clonidine