PMID: 2492443Jan 2, 1989Paper

Growth hormone releasing factor depolarizes rat pituitary cells in Na+-dependent mechanism

Brain Research
M Kato, M Suzuki

Abstract

Human growth hormone releasing factor (hGRF) is a specific stimulator of growth hormone (GH) secretion from somatotrophs both in vivo and in vitro. In this secretory process of GH adenosine 3',5'-cyclic monophosphate (cAMP) is thought to function as an intracellular mediator. The influx of Ca2+ from the extracellular space is indispensable for hGRF-induced GH secretion, which probably occurs through voltage-sensitive Ca2+ channels. We recently demonstrated that the extracellular Na+ is also essential for hGRF-induced GH secretion and proposed the possibility that hGRF depolarizes somatotrophs by increasing membrane Na+ conductance via cAMP, thereby activating voltage-sensitive Ca2+ channels, which in turn facilitate GH secretion. To directly demonstrate this possibility, we measured changes in both the membrane potentials and the intracellular Ca2+ concentration with fluorescent dyes bis-oxonol and fura 2 respectively and found that: (1) hGRF depolarized rat somatotrophs, (2) this hGRF-induced depolarization was greatly suppressed by replacing extracellular Na+ with mannitol or tris(hydroxymethyl)aminomethane (Tris+), but not by removing Ca2+ from the extracellular solution, and (3) hGRF augmented the intracellular Ca2+ concent...Continue Reading

Citations

Jul 1, 1994·Pflügers Archiv : European journal of physiology·A P NaumovB Hille
Apr 9, 1996·Regulatory Peptides·M KatoK Tatemoto
May 9, 2002·Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology·F Gracia-NavarroA J Martínez-Fuentes
Feb 24, 2001·Journal of Neurochemistry·S OhkumaT Ohgi
May 19, 2011·American Journal of Physiology. Endocrinology and Metabolism·Melanija TomićStanko S Stojilkovic
May 9, 2012·Journal of Neuroendocrinology·S S StojilkovicC A Stratakis
Oct 27, 1999·Canadian Journal of Physiology and Pharmacology·A PetitB T Lussier
Jun 1, 1996·The American Journal of Physiology·K TakanoN Yamashita
Oct 15, 1990·Biochemical and Biophysical Research Communications·H SoyaM Kato

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