Endocrinology, Vol 124, 2509-2518, Copyright © 1989 by Endocrine Society

ARTICLES

Evidence that gonadotropin-releasing hormone also functions as a growth hormone-releasing factor in the goldfish

TA Marchant, JP Chang, CS Nahorniak and RE Peter
Department of Zoology, University of Alberta, Edmonton, Canada.

The present study examined the influence of GnRH on the in vivo and in vitro secretion of GH in the goldfish (Carassius auratus). Intraperitoneal injection of several GnRH peptides, including a form native to goldfish, salmon GnRH (sGnRH), elevated circulating GH levels in female goldfish. An analog of mammalian GnRH (mGnRH), [D-Ala6,Pro9- NEt] mGnRH (mGnRH-A), at a dosage of 0.1 microgram/g BW increased serum GH levels for up to 48 h after a single ip injection. Goldfish receiving a series of injections of this dose of mGnRH-A also displayed an increased rate of body growth, indicating that the mGnRH-A-induced increase in the circulating GH level was sufficient to accelerate body growth. In vitro experiments using perifused pituitary fragments found that sGnRH stimulated the secretion of GH from the goldfish pituitary in a potent, dose-dependent, and reversible manner. The time course of response and half-maximally effective dose of sGnRH were very similar for both GH and gonadotropin (GTH) secretion in vitro, suggesting that the mechanism(s) mediating the stimulatory actions of GnRH in the goldfish may be similar for both GH and GTH secretion. However, GnRH- induced GH and GTH secretion from the goldfish pituitary can occur independently of each other, as demonstrated by the finding that somatostatin inhibited the GnRH stimulation of GH secretion in vitro, without influencing the GTH response, whereas the dopamine agonist apomorphine inhibited GnRH-induced GTH secretion in vitro, without influencing the GH response. Furthermore, the dopamine antagonist pimozide did not influence serum GH levels, although pimozide potentiated the stimulatory effect of GnRH on GTH secretion in vivo by blocking the endogenous GTH release inhibitory action of dopamine. Results of the present study suggest that the secretion of GH and GTH in the goldfish are regulated, at least in part, through a common releasing factor, GnRH, whereas somatostatin and dopamine appear to act independently as GH and GTH release inhibitory factors, respectively.

This article has been cited by other articles:

				A. L Filby, R. v. Aerle, J. Duitman, and C. R Tyler The Kisspeptin/Gonadotropin-Releasing Hormone Pathway and Molecular Signaling of Puberty in Fish Biol Reprod, February 1, 2008; 78(2): 278 - 289. [Abstract] [Full Text] [PDF]

				C. A. Flanagan, C.-C. Chen, M. Coetsee, S. Mamputha, K. E. Whitlock, N. Bredenkamp, L. Grosenick, R. D. Fernald, and N. Illing Expression, Structure, Function, and Evolution of Gonadotropin-Releasing Hormone (GnRH) Receptors GnRH-R1SHS and GnRH-R2PEY in the Teleost, Astatotilapia burtoni Endocrinology, October 1, 2007; 148(10): 5060 - 5071. [Abstract] [Full Text] [PDF]

				T. Ikemoto and M. K. Park Comparative analysis of the pituitary and ovarian GnRH systems in the leopard gecko: signaling crosstalk between multiple receptor subtypes in ovarian follicles J. Mol. Endocrinol., February 1, 2007; 38(2): 289 - 304. [Abstract] [Full Text] [PDF]

				A. O. L. Wong, M. C. Y. Chuk, H. C. Chan, and E. K. Y. Lee Mechanisms for gonadotropin-releasing hormone potentiation of growth hormone rebound following norepinephrine inhibition in goldfish pituitary cells Am J Physiol Endocrinol Metab, January 1, 2007; 292(1): E203 - E214. [Abstract] [Full Text] [PDF]

				C. Klausen, T. Tsuchiya, J. P. Chang, and H. R. Habibi PKC and ERK are differentially involved in gonadotropin-releasing hormone-induced growth hormone gene expression in the goldfish pituitary Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2005; 289(6): R1625 - R1633. [Abstract] [Full Text] [PDF]

				N. Moncaut, G. Somoza, D. M Power, and A. V M Canario Five gonadotrophin-releasing hormone receptors in a teleost fish: isolation, tissue distribution and phylogenetic relationships J. Mol. Endocrinol., June 1, 2005; 34(3): 767 - 779. [Abstract] [Full Text] [PDF]

				I. S. Parhar, S. Ogawa, and Y. Sakuma Three GnRH receptor types in laser-captured single cells of the cichlid pituitary display cellular and functional heterogeneity PNAS, February 8, 2005; 102(6): 2204 - 2209. [Abstract] [Full Text] [PDF]

				H. Zhou, X. Wang, W. K. W. Ko, and A. O. L. Wong Evidence for a Novel Intrapituitary Autocrine/Paracrine Feedback Loop Regulating Growth Hormone Synthesis and Secretion in Grass Carp Pituitary Cells by Functional Interactions between Gonadotrophs and Somatotrophs Endocrinology, December 1, 2004; 145(12): 5548 - 5559. [Abstract] [Full Text] [PDF]

				L. Huo, E. K. Y. Lee, P. C. Leung, and A. O. L. Wong Goldfish Calmodulin: Molecular Cloning, Tissue Distribution, and Regulation of Transcript Expression in Goldfish Pituitary Cells Endocrinology, November 1, 2004; 145(11): 5056 - 5067. [Abstract] [Full Text] [PDF]

				S. Unniappan and R. E. Peter In vitro and in vivo effects of ghrelin on luteinizing hormone and growth hormone release in goldfish Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2004; 286(6): R1093 - R1101. [Abstract] [Full Text] [PDF]

				D. Gonzalez-Martinez, T. Madigou, E. Mananos, J. M. Cerda-Reverter, S. Zanuy, O. Kah, and J. A. Munoz-Cueto Cloning and Expression of Gonadotropin-Releasing Hormone Receptor in the Brain and Pituitary of the European Sea Bass: An In Situ Hybridization Study Biol Reprod, May 1, 2004; 70(5): 1380 - 1391. [Abstract] [Full Text] [PDF]

				E. D. Vickers, F. Laberge, B. A. Adams, T. J. Hara, and N. M. Sherwood Cloning and Localization of Three Forms of Gonadotropin-Releasing Hormone, Including the Novel Whitefish Form, in a Salmonid, Coregonus clupeaformis Biol Reprod, April 1, 2004; 70(4): 1136 - 1146. [Abstract] [Full Text] [PDF]

				B. A. Adams, E. D. Vickers, C. Warby, M. Park, W. H. Fischer, A. Grey Craig, J. E. Rivier, and N. M. Sherwood Three Forms of Gonadotropin-Releasing Hormone, Including a Novel Form, in a Basal Salmonid, Coregonus clupeaformis Biol Reprod, July 1, 2002; 67(1): 232 - 239. [Abstract] [Full Text] [PDF]

				N. Scanlan and D. C. Skinner Estradiol Modulation of Growth Hormone Secretion in the Ewe: No Growth Hormone-Releasing Hormone Neurons and Few Somatotropes Express Estradiol Receptor {alpha} Biol Reprod, May 1, 2002; 66(5): 1267 - 1273. [Abstract] [Full Text]

				Y. K. Narnaware, P. P. Peyon, X. Lin, and R. E. Peter Regulation of food intake by neuropeptide Y in goldfish Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2000; 279(3): R1025 - R1034. [Abstract] [Full Text] [PDF]

				J. Carolsfeld, J. F. F. Powell, M. Park, W. H. Fischer, A. G. Craig, J. P. Chang, J. E. Rivier, and N. M. Sherwood Primary Structure and Function of Three Gonadotropin-Releasing Hormones, Including a Novel Form, from an Ancient Teleost, Herring Endocrinology, February 1, 2000; 141(2): 505 - 512. [Abstract] [Full Text] [PDF]

				V. Trudeau, O Kah, J. Chang, B. Sloley, P Dubourg, E. Fraser, and R. Peter The inhibitory effects of (gamma)-aminobutyric acid (GABA) on growth hormone secretion in the goldfish are modulated by sex steroids J. Exp. Biol., January 5, 2000; 203(9): 1477 - 1485. [Abstract] [PDF]

				X. Lin, C. J. Otto, and R. E. Peter Expression of Three Distinct Somatostatin Messenger Ribonucleic Acids (mRNAs) in Goldfish Brain: Characterization of the Complementary Deoxyribonucleic Acids, Distribution and Seasonal Variation of the mRNAs, and Action of a Somatostatin-14 Variant Endocrinology, May 1, 1999; 140(5): 2089 - 2099. [Abstract] [Full Text]

				N. Illing, B. E. Troskie, C. S. Nahorniak, J. P. Hapgood, R. E. Peter, and R. P. Millar Two gonadotropin-releasing hormone receptor subtypes with distinct ligand selectivity and differential distribution in brain and pituitary in the goldfish (Carassius auratus) PNAS, March 2, 1999; 96(5): 2526 - 2531. [Abstract] [Full Text] [PDF]

				P. Melamed, G. Gur, H. Rosenfeld, A. Elizur, and Z. Yaron Possible Interactions between Gonadotrophs and Somatotrophs in the Pituitary of Tilapia: Apparent Roles for Insulin-Like Growth Factor I and Estradiol Endocrinology, March 1, 1999; 140(3): 1183 - 1191. [Abstract] [Full Text]

				A. O. L. Wong, M. Y. Leung, W. L. C. Shea, L. Y. Tse, J. P. Chang, and B. K. C. Chow Hypophysiotropic Action of Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) in the Goldfish: Immunohistochemical Demonstration of PACAP in the Pituitary, PACAP Stimulation of Growth Hormone Release from Pituitary Cells, and Molecular Cloning of Pituitary Type I PACAP Receptor Endocrinology, August 1, 1998; 139(8): 3465 - 3479. [Abstract] [Full Text] [PDF]

				H. J.TH. GOOS, M. BLOMENROHR, J. BOGERD, P. T. BOSMA, K. W. LI, K. OKUZAWA, F. E.M. REBERS, R. W. SCHULZ, C. P. TENSEN, and M. A. ZANDBERGEN Gonadotropin-Releasing Hormones and Their Receptors in Fish Ann. N.Y. Acad. Sci., May 15, 1998; 839(1): 41 - 46. [Full Text] [PDF]

				A. S. Penzias, S. R. Goodman, G. Rossi, F. N. Shamma, R. F. Aten, H. R. Behrman, and E. E. Jones Preliminary Evidence That GnRH Has the Properties of a Growth Hormone-Releasing Factor In Vivo in the Rat Reproductive Sciences, July 1, 1995; 2(4): 623 - 629. [Abstract] [PDF]