Differential modulation of ghrelin-induced GH and LH release by PACAP and dopamine in goldfish pituitary cells

作者：Grey Caleb L; Chang John P^*

来源：General and Comparative Endocrinology, 2013, 191: 215-224.

DOI：10.1016/j.ygcen.2013.06.020

• Goldfish ghrelin
• Fura-2/AM calcium imaging
• Signal transduction
• Primary goldfish pituitary cell culture
• Maturational gonadotropin GTH-II

Ghrelin (GRLN) participates in multiple physiological processes, including the regulation of growth hormone (GH) and luteinizing hormone (LH) release. In the goldfish, neuroendocrine control of GH and LH release are multifactorial. In this system, pituitary adenylate cyclase-activating polypeptide (PACAP)-stimulated GH and LH secretion, as well as dopamine (DA)-induced GH release, are mediated by protein kinase A (PKA)-dependent, but protein kinase C (PKC)-independent, mechanisms. In addition, DA inhibits LH secretion by actions at sites along both PICA and PKC signaling pathways. Recently, goldfish GRLN (gGRLN(19)) has been shown to induce GH release via PKC, and LH secretion via both PKC and PICA. To further understand the neuroendocrine regulation of goldfish GH and LH release, we examined the effects of DA and PACAP on gGRLN(19) actions in primary cultures of goldfish pituitary cells in perifusion and in Ca2+-imaging experiments. Consistent with their known intracellular signaling mechanisms in gonadotrophs, DA inhibited gGRLN(19)-induced LH release while cotreatment of PACAP and gGRLN(19) did not produce additive LH responses. When applied prior to gGRLN(19), PACAP potentiated gGRLN(19)-induced GH release and Ca2+ signals within somatotrophs. In contrast, neither prior treatment with DA followed by gGRLN(19) nor pretreatment with gGRLN(19) prior to PACAP produced an enhanced GH release response. These observations suggest that PICA activators positively modulate gGRLN(19) actions on goldfish somatotrophs in a ligand- and treatment order-specific manner. Results add to our understanding of the complexity of neuroendocrine control of GH and LH release at the pituitary cell level, and our understanding of GRLN action.

• 出版日期2013-9-15