Inhibitory action of the alpha 1-adrenergic receptor on growth hormone secretion in the dog.
Intravenous administration of methoxamine ( METHOX , 5 mg, iv), a specific alpha 1-adrenergic agonist, reduced baseline GH levels of four unanesthetized beagle dogs 45 and 60 min post-injection and completely abolished the GH-releasing effect of the alpha 2-adrenergic agonist clonidine ( CLON , 4/ micrograms/kg, iv). Prazosin (PRA, 0.1 mg/kg, iv), an alpha 1-adrenergic antagonist, administered before METHOX re-instituted the GH-releasing effect of CLON . METHOX administered at the starting of an arginine infusion (ARG, 10% solution, 3.3 ml/min X 30 min) reduced consistently the GH releasing effect of the latter while, conversely, pretreatment with PRA, strikingly potentiated the GH-releasing effect of the amino acid (2 dogs). METHOX did not alter the GH-releasing effect of human pancreatic GH-releasing factor (hpGRF-40, 1/microgram/kg, iv), though it consistently delayed the occurrence of the GH secretory peak following hpGRF-40. These data indicate that alpha 1-adrenergic receptors located in the central nervous system, inhibit in the dog tonic and stimulated GH secretion.
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D004285:Dogs; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*
D011943:Receptors, Adrenergic, beta; D013006:Growth Hormone; D001120:Arginine; D008729:Methoxamine; D003000:Clonidine; D011224:Prazosin