Neurotransmitter Receptor Agonists Regulate Growth Hormone Gene Expression in Cultured Ovine Pituitary Cells

AbstractThe regulation of growth hormone (GH) secretion and GH mRNA content by the dopaminergic agonist, bromocriptine (BRO); the β-adrenergic agonist; isoproterenol (ISO); the α1-adrenergic agonist, methoxamine (MET); the α2-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 (10-6M) inhibited basal and GHRH (10-10M)-stimulated GH release. Bromocriptine enhanced GH mRNA content and potentiated the GHRH (10-8M)-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 (10-6M) 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 (10-7M) inhibited GHRH-stimulated GH secretion and GH mRNA accumulation. These results support the hyp...