Abstract
In this investigation, we studied the effects of Momany peptide (GHRP-5), on somatotroph secretory activity. Acute and chronic administration of GHRP-5 provokes a significant release of growth hormone that can be closely correlated with ultrastructural changes in somatotroph populations. After 3, 5 and 7 days of GHRP-5 treatment, two somatotroph cell subpopulations coexist. One of them has an enhanced secretory activity and the other presents a quiescent appearance. Therefore, pituitary growth hormone content was not affected in the first seven days of GHRP-5 treatment. After 14 days, there was a significant depletion of growth hormone pituitary content coincident with the highest levels of serum growth hormone. These results concur with the surge of a new hyperactive somatotroph subtype characterised by numerous immature secretory granules that are discharged bypassing the maturation step. Acute and chronic treatments caused no changes in somatotroph cell density, the area immunostained for growth hormone and the levels of total mRNA for transcription factor pit-1.
The results of pituitary cell cultures incubated with specific blockers for different signalling pathways demonstrated an involvement of the phospholipase C–inositol phosphate system in GHRP-5 stimulated somatotroph secretion.
GHRP-5 treatment enhanced significantly the release of growth hormone, thereby eliciting ultrastructural modifications in somatotrophs that can be correlated with an increased secretory activity devoid of cell density changes.
Similar content being viewed by others
References
Adams EF, Petersen B, Lei T, Buchfelder M, Fahlbusch R (1995) The growth hormone secretagogue, L-692429, induces phosphatidylinositol hydrolysis and hormone secretion by human pituitary tumors. Biochem Biophys Res Commun 208: 555–561.
Adams EF, Huang B, Buchfelder M, Howard A, Smith RG, Feighner SD, Van Der Ploeg LHT, Bowers CY, Fahlbusch R (1998) Presence of growth hormone secretagogue receptor messenger ribonucleic acid in human pituitary tumors and rat GH3 cells. J Clin Endocrinol Metab 83: 638–642.
Bertherat J, Bluet-Pajot MT, Epelbaum J (1995) Neuroendocrine regulation of growth hormone. Eur J Endocrinol 132: 12–24.
Bilezikjian LM, Erlichman J, Fleischer N, Vale W (1987) Differential activation of Type I and Type II 3′,5′-cyclic adenosine monophosphatedependent protein kinases by growth hormone releasing factor. Mol Endocrinol 1: 137–146.
Billestrup N, Larry W, Swanson LW, Wylie V (1986) Growth hormonereleasing factor stimulates proliferation of somatotrophs in vitro. Proc Natl Acad Sci USA 83: 6854–6857.
Billestrup N, Mitchell RL, Vale W, Verma IM (1987) Growth hormonereleasing factor induces c-fos expression in cultured primary pituitary cells. Mol Endocrinol 1: 300–305.
Bonaterra M, De Paul A, Aoki A, Torres A (1998) Residual effects of thyroid hormone on secretory activity of somatotroph population. Exp Clin Endocrinol Diabetes 106: 494–499.
Bowers CY, Sartor AA, Reynolds DG, Badger TAM (1991) On the actions of the growth hormone-releasing hexapeptide, GHRP-6. Endocrinology 128: 2027–2035.
Casanueva FF, Dieguez C (1999) Growth Hormone secretagogues: Physiological role and clinical utility. Trends Endocrinol Metab 10: 30–38.
Castrillo JL, Theill LE, Karin M (1991) Function of homeodomain protein GHF-1 in pituitary cell proliferation. Science 253: 197–199.
Chen C, Wu D, Clarke IJ (1996) Signal transduction systems employed by syntheticGHreleasing peptides in somatotrophs. J Endocrinol 148: 381–386.
Chen C (2001) Growth hormone secretagogue actions on the pituitary gland: Multiple receptors for multiple ligands? Clin Exp Pharmacol Physiol 27: 323–329.
Chomczynski P, Sacchi N (1987) Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. Anal Biochem 162: 156–159.
Danscher G, Ryter-Norgard JA (1983) Light microscopic visualization of colloidal gold on resin-embedded tissue. J Histochem Cytochem 31: 1394–1398.
De Paul AL, Pons P, Aoki A, Torres A (1997) Different behavior of lactotroph cell subpopulations in response to angiotensin II and thyrotrophin-releasing hormone. Cell Mol Neurobiol 17(2): 245–258.
Diaz Gavier MF, Aoki A, Orgnero De Gaisán E (1999) Prolactin secretory bypath exposed in cultured lactotrophs. Histochem J 31: 661–670.
Fourney RM, Miyakoshi J, Day III RS, Patterson MC (1988) Northern Blotting: efficient RNA staining and transfer. Focus 10: 5–7.
Griffiths G(1998) Quantitative aspects of immunocytochemistry. In:Fine structure Immunocytochemistry. Berlin, Heidelberg: Springer-Verlag, pp. 371–45.
Haggi E, Torres AI, Maldonado CA, Aoki A (1986) Regression of redundant lactotrophs in rat pituitary gland after cessation of lactation. J Endocrinol 111: 367–373.
Herrington J, Hille B (1994) Growth hormone-releasing hexapeptide elevates intracellular calcium in rat somatotrophs by two mechanisms. Endocrinology 135: 1100–1108.
Howard AD, Feighner SD, Cully DF, Arena JP, Liberator PA, Rosenblum CI, Hamelin M, Hreniuk DL, Palyha OC, Anderson J, Paress PS, Diaz C, Chou M, Liu KK, Mckee KK, Pong SS, Chaung LY, Elbrecht A, Dashkevicz M, Heavens R, Rigby M, Sirinathsinghji DJ, Dean DC, Melillo DG (1996) Areceptor in pituitary and hypothalamus that functions in growth hormone release. Science 273: 974–977.
Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H, Kangawa K (1999) Ghrelin is a growth hormone-releasing acylated peptide from stomach. Nature 402: 656–660.
Korbonits M, Grossman AB (1995) Growth Hormone releasing peptide and its analogues. Novel stimuli to Growth Hormone release. Trends Endocrinol Metab 6: 43–49.
Lei T, Buchfelder M, Fahlbusch R, Adams EF (1995) Growth hormone releasing peptide (GHRP-6) stimulates Phosphatidylinositol (PI) turnover in human pituitary somatotroph cells. J Mol Endocrinol 14: 135–138.
Maldonado CA, Aoki A (1986) Influence of embedding media in prolactin labeling with immunogold techniques. Histochem J 18: 429–433.
Mckee KK, Palyha OC, Feighner SD, Hrniuk DL, Tan CP, Phillips MS, Smith RG, Van Der Ploeg LHT, Howard AD (1997) Molecular analysis of growth hormone secretagogue receptors (GHS-Rs): Cloning of rat pituitary and hypothalamic GHS-R type 1a cDNAs. Mol Endocrinol 11: 415–423.
Momany FA, Bowers CY, Reynolds GA, Chang D, Hong A, Newlander K (1981) Design, synthesis and biological activity of peptides which release growth hormone in vitro. Endocrinology 108: 31–39.
Pellizas CG, Coleoni AH, Costamagna ME, Di Fulvio M, Masini-Repiso AM (1998) Insulin-like growth factor I reduces thyroid hormone receptors in rat liver. Evidence for a feed-back loop regulating the peripheral thyroid hormone action. J Endocrinol 158: 87–95.
Pellizas CG, Bonaterra M, De Paul AL, Aoki A Coleoni AH, Torres AI (2000) Somatotroph response to periodical IGF-I administration to male rats. Acta Histochem 102: 439–451.
Radovick S, Cohen LE, Wondisford FE (1998) The molecular basis of hypopituitarism. Horm Res 49: 30–36. Smallridge RC, Kiang JC, Gist ID, Fein HG, Galloway RJ (1992) U-73122, an aminosteroid phospholipase C antagonist, noncompetitively inhibits thyrotropin-releasing hormone effects in GH3 rat pituitary cells. Endocrinology 131: 1883–1888.
Smith RG, Cheng K, Schoen WR, Pong SS, Hickey G, Jacks T, Butler B, Chan WW, Chaung LY, Judith F (1993) Anonpeptidyl growth hormone secretagogue. Science 260: 1640–1643.
Smith RG, Van Der Ploeg LH, Howard AD, Feighner SD, Cheng K, Hickey GJ, Wyvratt MJ, Fisher MH, Nargund RP, Patchett AA (1997) Peptidomimetic regulation of growth hormone secretion. Endocr Rev 18: 621–645.
Snyder G, Hyner WC, Snyder J (1977) Functional heterogenity in somatotrophs isolated from the rat anterior pituitary. Endocrinology 101: 788–799.
Soto JL, Castrillo JL, Dominguez F, Dieguez C (1995) Regulation of the pituitary-specific transcription factor GHF-1/Pit-1 messenger ribonucleic acid levels by Growth Hormone secretagogues in rat anterior pituitary cells in monolayer culture. Endocrinology 136: 3863–3870.
Tiupakov AN, Brook CD, Pringle PJ, Peterkova VA, Volevodz NN, Bowers CY (1995) GH responses to intravenous bolus infusions of GH releasing hormone and GH releasing peptide 2 separately and in combination in adult volunteers. Clin Endocrinol 43: 347–350.
Torres AI, Aoki A (1987) Release of big and small molecular forms of prolactin: Dependence upon dynamic state of the lactotroph. J Endocrinol 114: 213–220.
Torres AI, Pasolli HA, Maldonado CA, Aoki A (1995) Changes in thyrotroph and somatotroph population induced by stimulation and inhibition of their secretory activity. Histochem J 27: 370–337.
Wu D, Chen C, Zhang J, Bowers CY, Clarke IJ (1996) The effects of GH-releasing peptide-6 (GHRP-6) and GHRP-2 on intracellular adenosine 3′,5′-monophosphate (cAMP) levels and GH secretion in ovine and rat somatotrophs. J Endocrinol 148: 197–205.
Wu D, Clarke J, Chen C (1997) The role of protein kinase C in GH secretion induced by GH-releasing factor and GH-releasing peptides in cultured ovine somatotrophs. J Endocrinol 154: 219–230.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Bonaterra, M., De Paul, A.L., Pellizas, C.G. et al. Behaviour of a Somatotroph Population Under a Growth Hormone Releasing Peptide Treatment. Histochem J 33, 675–683 (2001). https://doi.org/10.1023/A:1016310602813
Issue Date:
DOI: https://doi.org/10.1023/A:1016310602813