Alpha-2-adrenergic pathways release growth hormone via a non-GRF-dependent mechanism in normal human subjects.
Administration of a supramaximal dose of GRF 1-44 (200 micrograms, i.v.) to normal human volunteers increased GH levels while a further bolus of GRF (200 micrograms i.v.) given 2 hours later failed to increase plasma GH levels. In contrast, alpha-adrenergic receptor agonism with either propranolol-adrenaline infusion or clonidine increased plasma GH levels at a time when GH responses to this supramaximal dose of GRF were absent. This indicates that alpha-adrenergic pathways stimulate GH secretion through a non-GRF-dependent mechanism in normal human subjects.
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2a Divisione di Medicina Generale, Arcispedale, S. Maria Nuova, Reggio Emilia, Italy.
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D000328:Adult; D003000:Clonidine / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*
D011942:Receptors, Adrenergic, alpha; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D011433:Propranolol; D003000:Clonidine; D004837:Epinephrine