title: Neurotransmitter receptor agonists regulate growth hormone gene expression in cultured ovine pituitary cells.
abstract: The regulation of growth hormone (GH) secretion and GH mRNA content by the dopaminergic agonist, bromocriptine (BRO); the beta-adrenergic agonist; isoproterenol (ISO); the alpha 1-adrenergic agonist, methoxamine (MET); the alpha 2-adrenergic agonist, clonidine (CLON); the serotonergic agonist, quipazine (QUIP); somatostatin (SS) and GH-releasing hormone (GHRH) were studied using cultured ovine anterior pituitary cells. Clonidine and BRO (10(-6) M) inhibited basal and GHRH (10(-10) M)-stimulated GH release. Bromocriptine enhanced GH mRNA content and potentiated the GHRH (10(-8) M)-stimulated content of GH mRNA, while CLON had no effect on GH mRNA. Quipazine had little effect on GH secretion and no effect on GH mRNA content. Methoxamine and ISO (10(-6) M) increased basal secretion of GH and both enhanced GHRH-stimulated GH secretion. Both MET and ISO increased GH mRNA content of cultured ovine pituitary cells. Somatostatin (10(-7) M) inhibited GHRH-stimulated GH secretion and GH mRNA accumulation. These results support the hypothesis that neurotransmitters may regulate or interact to further modulate pituitary hormone release. Moreover, the data indicate that neurotransmitters may not only regulate secretion but also regulate GH mRNA content and thus affect hormone synthesis.
authors.affiliation: Department of Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Alabama 36849-5520.
authors.forename: E O
authors.initials: EO
authors.lastname: Soyoola
authors.forename: M F
authors.initials: MF
authors.lastname: Burgess
authors.forename: R C
authors.initials: RC
authors.lastname: Bird
authors.forename: R J
authors.initials: RJ
authors.lastname: Kemppainen
authors.forename: J C
authors.initials: JC
authors.lastname: Williams
authors.forename: J L
authors.initials: JL
authors.lastname: Sartin
mesh_terms: D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D013006:Growth Hormone / Q000235:genetics*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D010902:Pituitary Gland / Q000502:physiology*; D011814:Quipazine / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D012756:Sheep
chemical_list: D018377:Neurotransmitter Agents; D012333:RNA, Messenger; D001971:Bromocriptine; D011814:Quipazine; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D008729:Methoxamine; D007545:Isoproterenol; D003000:Clonidine