Advanced SearchSearch Tips
Somatotropic Axis and Nutrition in Young Ruminants around Weaning Time
facebook(new window)  Pirnt(new window) E-mail(new window) Excel Download
 Title & Authors
Somatotropic Axis and Nutrition in Young Ruminants around Weaning Time
Katoh, K.; Takahashi, T.; Kobayashi, Y.; Obara, Y.;
  PDF(new window)
The somatotropic (GH-IGF-I) axis consists of many hormonal and nutritional factors that control GH release from the somatotrophs in the anterior pituitary. The GH-releasing substances are GHRH and GHS (GHRP or ghrelin), while the GH release-inhibiting substances are somatostatin (SRIF), insulin-like growth factor-I (IGF-I), leptin and glucocorticoids. However, there is evidence showing that nutrition is involved in the control of the somatotropic axis. In addition, weaning is a drastic event for neonates because their alimentary and endocrine circumstances are changed due to the switch, even if gradual, from a liquid milk diet to one composed of such solids as hay and grains. The biological role of ghrelin is one of the hormonal factors that have been focused on ever since ghrelin was discovered at the end of the last century. A 27-amino acid peptide that is mainly synthesized and released from the abomasum epithelium, ghrelin has not been fully evaluated in relation to the somatotropic axis of the ruminant. It has also proven difficult even to investigate the cellular mechanisms of ghrelin action, because this hormone exerts animal-species-dependent actions via a complex set of intracellular signaling pathways. This is also the case for the action of leptin. Another substance, IGF-I, shows a partial inhibitory action on GH secretion in the ruminant. The effect of nutrition is also different among animal species. This is evident by the fact that undernutrition suppresses the circulating GH levels in rodents, but increases it in ruminants and humans. Recently, weaning has been shown to change the postprandial GH responses in ruminants; milk feeding increases, but hay and concentrate feeding suppress, the postprandial circulating GH levels. Even if the postprandial GH level is increased, the ghrelin level is decreased by milk feeding. Macronutrients also possess stimulatory and inhibitory actions on GH secretion in vivo and in vitro. These findings indicate the complexity of the control mechanisms of the somatotropic axis. In the present review, we summarize recent findings on the factors controlling the axis of the ruminant.
Ruminant;Somatotropic Axis;Nutrition;Weaning;Development;
 Cited by
Effects of Perinatal Nutrition on Metabolic and Hormonal Profiles of Goat Kids (Capra hircus) during Their First Day of Life,;;;;

아세아태평양축산학회지, 2008. vol.21. 11, pp.1585-1591 crossref(new window)
Effects of Na-butyrate supplementation in milk formula on plasma concentrations of GH and insulin, and on rumen papilla development in calves, Journal of Endocrinology, 2011, 211, 3, 241  crossref(new windwow)
Ghrelin, insulin and pancreatic activity in the peri-weaning period of goat kids, Journal of Animal Physiology and Animal Nutrition, 2011, 95, 1, 40  crossref(new windwow)
Establishment and characterization of dairy cow growth hormone secreting anterior pituitary cell model, In Vitro Cellular & Developmental Biology - Animal, 2014, 50, 2, 103  crossref(new windwow)
Aguilar, E., M. Tena-Sempere and L. Pinilla. 2005. Role of excitatory amino acids in the control of growth hormone. Endo. 28:295-302. crossref(new window)

Argente, J., L. M. Garcia-Segura, J. Pozo and J. A. Chowen. 1996. Growth hormone-releasing peptides: clinical and basic aspects. Horm. Res. 46:155-159. crossref(new window)

Barb, C. R., R. M. Campbell, J. D. Armstrong and N. M. Cox. 1996. Aspartate and glutamate modulation of growth hormone secretion in the pig: possible site of action. Domest. Anim. Endocrinol. 13:81-90. crossref(new window)

Barb, C. R., G. M. Derochers, B. Johnson, R. V. Utley, W. J. Chang, G. B. Rampacek and R. R. Kraeling. 1992. N-methyl-D, Laspartate stimulates growth hormone and prolactin but inhibits luteinizing hormone secretion in the pig. Domest. Anim. Endocrinol. 9:225-232. crossref(new window)

Baranowska, B., E. Wolinska-Witort, E. Wasilewska-Dziubinska, K. Roguski, L. Martynska and M. Chmielowska. 2003. The role of neuropeptides in the disturbed control of appetite and hormone secretion in eating disorders. Neuroendocrinol. Lett. 24:431-434.

Baumrucker, C. R., D. L. Hadsell and J. W. Blum. 1994. Effects of dietary insulin-like growth factor I on growth and insulin-like growth factor receptors in neonatal calf intestine. J. Anim. Sci. 72:428-433. crossref(new window)

Bassett, J. M. 1974a. Early changes in plasma insulin and growth hormone levels after feeding in lambs and adult sheep. Aust. J. Biol. Sci. 27:157-166. crossref(new window)

Bassett, J. M. 1974b. Diurnal patterns of plasma insulin, growth hormone, corticosteroid and metabolite concentrations in fed and fasted sheep. Aust. J. Biol. Sci. 27:167-181. crossref(new window)

Blake, A. D. and R. G. Smith. 1991. Desensitization studies using perifused rat pituitary cells show that growth hormone-releasing hormone and His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 stimulate growth hormone release through distinct receptor sites. J. Endocrinol. 129:11-19. crossref(new window)

Blanchard, M. M., C. G. Goodyer, J. Charrier and B. Barenton. 1988. In vitro regulation of growth hormone (GH) release from ovine pituitary cells during fetal and neonatal development: effects of GH-releasing factor, somatostatin, and insulin-like growth factor I. Endocrinol. 122:2114-2120. crossref(new window)

Blum, J. W. and H. Hammon. 1999. Endocrine and metabolic aspects in milk-fed calves. Domest. Anim. Endocrinol. 17:219-230. crossref(new window)

Bowers, C. Y. 1999. GHRP: unnatural toward the natural. In: Growth hormone secretagogues. (Ed. E. Ghigo, M. Boghen, F. F. Casanueva and C. Dieguez) Elsevier, Amsterdam, Netherlands. pp. 5-18.

Briard, N., A. Dutour, J. Epelbaum, N. Sauze, A. Slama and C. Oliver. 1997. Species differences between male rat and ram pituitary somatostatin receptors involved in the inhibition of growth hormone secretion. Eur. J. Endocrinol. 137: 545-555. crossref(new window)

Bronglio, F., A. Benso, C. Gottero, F. Prodam, S. Grottoli, F. Tassone, M. Maccario, F. F. Casanueva, C. Dieguez, R. Deghenghi, E. Ghigo and E. Arvat. 2002. Effects of glucose, free fatty acids or arginine load on the GH-releasing activity of ghrelin in humans. Clin. Endocrinol. 57:265-271. crossref(new window)

Casanueva, F. F., L. Villanueva, C. Dieguez, Y. Diaz, J. A. Cabranes, B. Szoke, M. F. Scanlon, A. V. Schally and A. Fernandez-Cruz. 1987. Free fatty acids block growth hormone (GH) releasing hormone-stimulated GH secretion in man directly at the pituitary. J. Clin. Endocrinol. Metab. 65:634-642. crossref(new window)

Chen, C., P. Farnworth, S. Petersenn, I. Musgrave, B. J. Canny and I. J. Clarke. 1998a. Growth-hormone-releasing peptide-2 (GHRP-2) does not act via the human growth hormonereleasing factor receptor in GC cells. Endocrine 9: 71-77. crossref(new window)

Chen, C., M. Pullar, K. Loneragan, J. Zhang and I. J. Clarke. 1998b. Effect of growth hormone-releasing peptide-2 (GHRP-2) and GH-releasing hormone (GHRH) on the cAMP levels and GH release from cultured acromegalic tumours. J. Neuroendocrinol. 10:473-480. crossref(new window)

Cheung, C. C., D. K. Clifton and R. A. Steiner. 1997. Proopiomelanocortin neurons are direct targets for leptin in the hypothalamus. Endocrinol. 138:4489-4492. crossref(new window)

Clark, P. A. and A. D. Rogol. 1999. Somatic growth and its regulation. In: Handbook of Physiology, Sec. 7, Vol. V. Hormonal control of growth. (Ed. J. L. Kostyo). American Physiological Society, Oxford University Press, New York, New York. pp. 37-72.

Clarke, I. J., T. Fletcher, C. C. Pomares, J. H. G. Holmes, F. Dunshea, G. B. Thomas, A. J. Tilbrook, P. E. Walton and D. B. Galloway. 1993. Effect of high-protein feed supplements on concentrations of growth hormone (GH), insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 in plasma and on the amounts of GH and messenger RNA for GH in the pituitary glands of adult rams. J. Endocrinol. 138:421-427. crossref(new window)

Clarke, I. J., B. Henry, J. Iqbal and J. W. Goding. 2001. Leptin and the regulation of food intake and the neuroendocrine axis in sheep. Clin. Exp. Pharmacol. Physiol. 28:106-107. crossref(new window)

Coxam, V., M. J. Davicco and J. P. Barlet. 1989. Effect of triglycerides on growth hormone (GH)-releasing factormediated GH secretion in newborn calves. Domest. Anim. Endocrinol. 6:389-393. crossref(new window)

Date, Y., Kojima, M. H. Hosoda, A. Sawaguchi, M. S. Mondal, T. Sugamura, S. Matsukura, K. Kanagawa and M. Nakazato. 2000. Ghrelin, a novel growth hormone-releasing acylated peptide, is synthesized in a distinct endocrine cell type in the gastrointestinal tracts or rats and humans. Endocrinol. 141:4255-4261. crossref(new window)

Downing, J. A., J. Joss and R. J. Scaramussi. 1996. The effects of N-methyl-D,L-aspartic acid and aspartic acid on the plasma concentration of gonadotropins, GH and prolactin in the ewe. J. Endocrinol. 149:65-72. crossref(new window)

Driver, P. M. and J. M. Forbes. 1981. Episodic growth hormone secretion in sheep in relation to time of feeding, spontaneous meals and short term fasting. J. Physiol. 317:412-424.

Englander, E. W., G. A. Gomez and G. H. Greeley Jr. 2004. Alterations in stomach ghrelin production and in ghrelin-induced growth hormone secretion in the aged rat. Mech. Ageing Develop. 125:871-875. crossref(new window)

Erdmann, J., F. Lippl and V. Schusdziarra. 2003. Differential effect of protein and fat on plasma ghrelin levels in man. Regl. Peptides 116:101-107. crossref(new window)

Estienne, M. J., K. V. and C. R. Bard. 2005. The control of adenohypophysial hormone secretion by amino acids and peptides in swine. Domest. Anim. Endocrinol. 29:34-42. crossref(new window)

Estienne, M. J., K. V. McElwain, J. B. Barrett and C. R. Bard. 1999. Effects of N-methyl-D, L-aspartate on secretion of growth hormone-releasing hormone from the boar hypothalamic-preoptic area and median eminence in vitro. Domest. Anim. Endocrinol. 17:403-407. crossref(new window)

Estienne, M. J., K. K. Schillo, M. A. Green and J. A. Boling. 1989a. Free fatty acids suppress growth hormone, but not luteinizing hormone, secretion in sheep. Endocrinol. 125:85-91. crossref(new window)

Estienne, M. J., K. K. Schillo, M. A. Green, S. M. Hileman and J. A. Boling. 1989b. N-methyl-D, L-aspartate stimulates growth hormone but not luteinizing hormone secretion in the sheep. Life Sci. 44:1527-1533. crossref(new window)

Fei, H., H. J. Okano, C. Li, G. H. Lee, C. Zhao, R. Darnell and J. M. Friedman. 1997. Anatomic localization of alternatively spliced leptin receptors (Ob-R) in mouse brain and other tissues. Proc. Natl. Acad. Sci. USA. 94:7001-7005 crossref(new window)

Fletcher, T. P., G. B. Thomas and I. J. Clarke. 1996. Growth hormone-releasing hormone and somatostatin concentrations in the hypophysial portal blood of conscious sheep during the infusion of growth hormone-releasing peptide-6. Domest. Anim. Endocrinol. 13:251-258. crossref(new window)

Fletcher, T. P., G. B. Thomas, F. R. Dunshea, L. G. Moore and I. J. Clarke. 1995. IGF feedback effects on growth hormone secretion in ewes: evidence for action at the pituitary but not the hypothalamic level. J. Endocrinol. 144:323-331. crossref(new window)

Frohman, L. A., T. R. Downs, I. J. Clarke and G. B. Thomas. 1990. Measurement of growth hormone-releasing hormone and somatostatin in hypothalamic-portal plasma of unanesthetized sheep. J. Clin. Invest. 86:17-24. crossref(new window)

Gatfold, K. L., T. P. Fletcher, A. Rao, A. R. Egan, B. J. Hosking and I. J. Clarke. 1997. GH, GH-releasing factor and somatostatin in the growing lamb: sex differences and mechanisms for sex differences. J. Endocrinol. 152:19-27. crossref(new window)

Gaynor, P. J., K. J. Lookingland and H. A. Tucker. 1995. 5-hydroxytryptaminergic receptor-stimulated growth hormone secretion occurs independently of changes in peripheral somatostatin concentration. Proc. Soc. Exp. Biol. Med. 209:79-85. crossref(new window)

Han, X. F., Y. L. Zhu, M. Hernandez, D. J. Keating and C. Chen. 2005. Ghrelin reduces voltage-gated potassium currents in GH3 cells via cyclic GMP pathways. Endoc. 28:217-224. crossref(new window)

Hanew, K. 2000. The mechanism of arginine- and insulin-induced GH release in humans. Endocr. J. 47(Suppl):S23-S27. crossref(new window)

Hartman, M. L., J. D. Veldhuis, M. L. Johnson, M. M. Lee, K. G. Alberti and E. Samojlik. 1992. Augmented growth hormone (GH) secretory burst frequency and amplitude mediate enhanced GH secretion during a two-day fast in normal men. J. Clin. Endocrinol. Metab. 74:757-765. crossref(new window)

Hashizume, T., M. Horiuchi, S. Nonaka, E. Kasuya, M. Kojima, H. Hosoda and K. Kangawa. 2005. Effects of ghrelin on growth hormone secretion in vivo in ruminants. Regul. Peptides 126:61-65. crossref(new window)

Hayashida, T., K. Murakami, K. Mogi, M. Nishihara, M. Nakazato. M. S. Mondal, Y. Horii, M. Kojima, K. Kangawa and N. Murakami. 2001. Ghrelin in domestic animals: distribution in stomach and its possible role. Domest. Anim. Endocrinol. 21:17-24. crossref(new window)

Henry, B. A., J. W. Goding, W. S. Alexander, A. J. Tilbrook, B. Canny, F. Dunshea, A. Rao, M. Mansell and I. J. Clarke. 1999. Central administration of leptin to sheep inhibits food intake without affecting the secretion of hormones from the pituitary gland; evidence for a dissociation of effects on appetite and neuroendocrine function. Endocrinol. 140:1175-1182. crossref(new window)

Henry, B. A., A. Rao, A. J. Tilbrook and I. J. Clarke. 2001. Chronic food-deprivation alters the expression of somatostatin and growth hormone-releasing hormone in the ovariectomized ewe. J. Endocrinol. 170: R1-R6. crossref(new window)

Hertelendy, F. and D. M. Kipnis. 1973. Studies on growth hormone secretion: V. Influence of plasma free fatty acid level. Endocrinol. 92:402-410. crossref(new window)

Howard, A. D., S. D. Feighner, D. F. Cully, J. P. Arena, P. A. Liberator, C. I. Rosenblum, M. Hamelin, D. L. Hreniuk, O. C. Palyha, J. Anderson, P. S. Paress, C. Diaz, M. Chou, K. K. Liu, K. K. McKee, S. S. Pong, L. Y. Chaung, A. Elbrecht, M. Dashkevicz, R. Heavens, M. Rigby, D. J. Sirinathsinghji, D. C. Dean, D. G. Melillo, A. A. Patchett, R. Nargund, P. R. Griffin, J. A. DeMartino, S. K. Gupta, J. A. Schaeffer, R. G. Smith and H. Van der Ploeg. 1996. A receptor in pituitary and hypothalamus that functions in growth hormone release. Sci. 273:974-977. crossref(new window)

Iqbal, J., Y. Kurose, B. Canny and I. J. Clarke. 2006. Effects of central infusion of ghrelin on food intake and plasma levels of growth hormone, luteinizing hormone, prolactin, and cortisol secretion in sheep. Endocrinol. 147:510-519. crossref(new window)

Ishiwata, H., M. Nagano, Y. Sasaki, C. Chen and K. Katoh. 2000. Short-chain fatty acids inhibit the release and content of growth hormone in anterior pituitary cells of the goat. Gen. Comp. Endocrinol. 118:400-406. crossref(new window)

Ishiwata, H., K. Katoh, C. Chen, T. Yonezawa, Y. Sasaki and Y. Obara. 2005. Suppressing actions of butyrate on growth hormone (GH) secretion induced by GH-releasing hormone in rat anterior pituitary cells. Gen. Comp. Endocrinol. 143:222-230. crossref(new window)

Ishizuka, B., M. E. Quigley and S. S. C. Yen. 1983. Pituitary hormone release in response to food ingestion: evidence for neuroendocine signals from gut to brain. J. Clin. Endocrinol. Metab. 57:1111-1116. crossref(new window)

Itoh, F., T. Komatsu, M. Yonai, T. Sugino, M. Kojima, K. Kangawa, Y. Hasegawa, Y. Terashima and K. Hodate. 2005. GH secretory responses to ghrelin and GHRH in growing and lactating dairy cattle. Domest. Anim. Endocrinol. 28:34-45. crossref(new window)

Jaffe, C. A., B. Ocampo-Lim, W. Guo, K. Krueger, I. Sugahara, R. DeMott-friberg, M. Ermann and A. Barkan. 1998. Regulatory mechanisms of growth hormone secretion are sexually dimorphic. J. Clin. Invest. 102:153-164. crossref(new window)

Kamegai, J., H. Tamura, T. Shimizu, S. Ishii, H. Sugihara and S. Oikawa. 2005. Insulin-like growth factor-I down-regulates ghrelin receptor expression in the rat pituitary. Regul. Peptides 127:203-206. crossref(new window)

Katoh, K., G. Furukawa, K. Kitade, N. Katsumata, Y. Kobayashi and Y. Obara. 2004a. Postprandial changes in plasma GH and insulin concentrations, and responses to stimulation with GH-releasing hormone (GHRH) and GHRP-6 in calves around weaning. J. Endocrinol. 183:497-505. crossref(new window)

Katoh, K. and H. Ishiwata. 1998. Changes in intracellular calcium concentration and growth hormone release induced by nutrients in primary cultured anterior pituitary cells of goats. Anim. Sci. Technol. (Jpn) 69:994-1003.

Katoh, K. and Y. Obara. 2001. Developmental and nutritional control of the somatotropic axis in the ruminant. Asian-Aust. J. Anim. Sci. 14(Special Issue): 91-99.

Katoh, K., Y. Ohata and H. Ishiwata. 1999. Suppressing effects of short-chain fatty acids on growth hormone (GH)-releasing hormone-induced GH release in isolated anterior pituitary cells of goats. Domest. Anim. Endocrinol. 17:85-93. crossref(new window)

Katoh, K., R. Shimoguchi, H. Ishiwata and Y. Obara. 2004b. Rapid suppressing action of insulin-like growth factor-I (IGF-I) on GH release from anterior pituitary cells of goats. Domest. Anim. Endocrinol. 26:177-188. crossref(new window)

Kojima, M., H. Hosoda, Y. Date, M. Nakazato, H. Matsuo and K. Kanagawa. 1999. Ghrelin is a novel growth-hormone-releasing acylated peptide from stomach. Nature 402:656-660. crossref(new window)

Kojima, M. and K. Kangawa. 2005. Ghrelin: structure and function. Physiol. Rev. 85:495-522. crossref(new window)

Kuhara, T., S. Ikeda, A. Ohneda and Y. Sasaki. 1991. Effects of intravenous infusion of 17 amino acids on the secretion of GH, glucagon, and insulin in sheep. Am. J. Physiol. 260:E21-E26.

Lindstrom, P. and L. Ohlsson. 1992. Effect of N-methyl-D, L-aspartate on isolated rat somatotrophs. Endocrinol. 131:1903-1907. crossref(new window)

Malagon, M. M., R. M. Luque, E. Ruiz-Guerrero, F. Rodriguez-Pacheco, S. Garcia-Navarro, F. F. Casanueva, F. Gracia-Navarro and J. P. Castano. 2003. Intracellular signaling mechanisms mediating ghrelin-stimulated growth hormone release in somatotropes. Endocrinol. 144:5372-5380. crossref(new window)

Matsunaga, N., N. T. Arakawa, T. Goka, K. T. Nam, A. Ohneda, Y. Sasaki and K. Katoh. 1999. Effects of ruminal infusion of volatile fatty acids on plasma concentration of growth hormone and insulin in sheep. Domest. Anim. Endocrinol. 17:17-27. crossref(new window)

Matsunaga, N., T. Goka, K. T. Nam, S. Oda, A. Ohneda and Y. Sasaki. 1997a. Inhibition of GH releasing factor (GRF)-induced GH secretion by intraruminal infusion of volatile fatty acids (VFA) in sheep. Endocrine J. 44: 133-140. crossref(new window)

Matsunaga, N., I. Kubota, S. G. Roh, M. L. He, S. Hidaka, H. Hidari and Y. Sasaki. 1997b. Effect of mesenteric venous volatile fatty acids (VFA) infusion on GH secretion in sheep. Endoc. J. 44:707-714. crossref(new window)

Matsunaga, N., K. T. Nam, T. Kuhara, S. Oda, A. Ohneda and Y. Sasaki. 1993. Inhibitory effect of volatile fatty acids on GRFinduced GH secretion in sheep. Endocrine J. 40:529-537. crossref(new window)

Matsunaga, N., M. Wakiya, S. G. Roh, M. Hirota, M. L. He, S. Hidaka and H. Hidari. 1998. Effect of cholinergic blockade on inhibited GH secretion by feeding and intraruminal SCFA infusion in sheep. Am. J. Physiol. 274:E45-E51.

Merimee, T. J. and S. E. Fineberg. 1974. Growth hormone secretion in starvation: a reassessment. J. Clin. Endocrinol. Metab. 39:385-386. crossref(new window)

Morash, B., A. Li, P. R. Murphy, M. Wilkinson and E. Ur. 1999. Leptin gene expression in the brain and pituitary gland. Endocrinol. 140:5995-5998. crossref(new window)

Mercer, J. G., N. Hoggard, L. M. Williams, C. B. Lawrence, L. T. Hannah, P. J. Morgan and P. trayhurn 1996. Coexpression of leptin receptor and neuropeptide Y mRNA in arcuate nucleus of mouse hypothalamus. J. Neuroendocrinol. 8:733-735. crossref(new window)

Morel, G., R. Gallego, L. Boulanger, E. Pintos, T. Garcia-Caballero and P. Gaudreau. 1999. Restricted presence of the growth hormone-releasing hormone receptor to somatotrophs in rat and human pituitaries. Neuroendocrinol. 70:128-136. crossref(new window)

Moseley, W. M., G. R. Alaniz, W. H. Claffin and L. F. Krabill. 1988. Food intake alters the serum growth hormone response to bovine growth hormone-releasing factor in meal-fed Holstein steers. J. Endocrinol. 117:253-259. crossref(new window)

Muller, E. E., V. Locatelli and D. Cocchi. 1999. Neuroendocrine control of growth hormone secretion. Physiol. Rev. 79:511-607. crossref(new window)

Nakagawa、E., N. Nagaya, H. Okumura, M. Enomoto, H. Oya, F. Ono, H. Hosoda, M. Kojima and K. Kangawa. 2002. Hyperglycaemia suppresses the secretion of ghrelin, a novel growth-hormone-releasing peptide: responses to the intravenous and oral administration of glucose. Clin. Sci. 103:325-328. crossref(new window)

Ohata, Y., Y. Maruyama, K. Katoh and Y. Sasaki. 1997. Growth hormone release induced by an amino acid mixture from primary cultured anterior pituitary cells of goats. Domest. Anim. Endocrinol. 14:99-107. crossref(new window)

Patchett, A. A., R. P. Nargund, J. R. Tata, M. H. Chen, K. J. Barakat, D. B. Johnston, K. Cheng, W. W. Chan, B. Butler and G. Hickey. 1995. Design and biological activities of L-163,191 (MK-0677): a potent, orally active growth hormone secretagogue. Proc. Natl. Acad. Sci. USA 92:7001-7005. crossref(new window)

Peino, R., F. Cordido, A. Penalva, C. Alvarez, C. Dieguez and F. F. Casanueva. 1996. Acipimox-mediated plasma free fatty acid depression per se stimulates growth hormone (GH) secretion in normal subjects and potentiates the response to other GHreleasing stimuli. J. Clin. Endocrinol. Metab. 81:909-913. crossref(new window)

Plouzek, C. A., J. R. Molina, D. L. Hard, W. W. Vale, J. Rivier, A. Trenkle and L. L. Anderson. 1988. Effects of growth hormonereleasing factor and somatostatin on growth hormone secretion in hypophysial stalk-transected beef calves. Proc. Soc. Exp. Bio. Med. 189:158-167. crossref(new window)

Reynaert, R., M. De Paepe, S. Marcus and G. Peeters. 1975. Influence of serum free fatty acid levels on growth hormone secretion in lactating cows. J. Endocrinol. 66:213-224. crossref(new window)

Rigamonti, A. E., A. I. Pincelli, B. Corra, R. Viarengo, S. M. Bonomo, D. Galimberti, M. Scacchi, E. Scarpini, F. Cavagnini and E. E. Muller. 2002. Plasma ghrelin concentrations in elderly subj ects: comparison with anorexic and obese patients. J. Endocrinol. 175:R1-R5. crossref(new window)

Roh, S.-G., I. J. Clarke, R.-W. Xu, J. W. Goding, K. Loneragan and C. Chen. 1998. The in vitro effect of leptin on basal and growth hormone-releasing hormone-stimulated growth hormone secretion from the ovine pituitary gland. Neuroendocrinol. 68:361-364. crossref(new window)

Romo, G. A., T. H. Elsasser, S. Kahl, R. A. Erdman and D. P. Casper. 1997. Dietary fatty acids modulate hormone responses in lactating cows: mechanistic role for 5'-deiodinase activity in tissue. Domest. Anim. Endocrinol. 14:409-420. crossref(new window)

Saleri, R., F. Grasselli and C. Tamanini. 2005. Effects of different culture conditions and leptin on GH mRNA expression and GH secretion by pig pituitary cells. Horm. Metab. Res. 37:214-219. crossref(new window)

Sartin, J. L., K. A. Cummins, R. J. Kemppainen, D. N. Marple, C. H. Rahe and J. C. Williams. 1985. Glucagon, insulin, and growth hormone responses to glucose infusion in lactating dairy cows. Am. J. Physiol., 248:E108-E114.

Senaris, R., C. X. Garcia-Caballero, R. Gallego, R. Castro, R. V. Considine, C. Dieguez and F. Casanueva. 1997. Synthesis of leptin in human placenta. Endocrinol. 138:4501-4504. crossref(new window)

Shimada, M., Y. Date, M. S. Mondal, K. Toshinai, T. Shimbara, K. Fukunaga, N. Murakami, M. Miyazato, K. Kangawa, H. Yoshimatsu, H. Matsuo and M. Nakazato. 2003. Somatostatin suppresses ghrelin secretion from the rat stomach. Biochem. Biophys. Res. Commun. 302:520-525. crossref(new window)

Silva, A. P., K. Bethmann, F. Raulf and H. A. Schmid. 2005. Regulation of ghrelin secretion by somatostatin analogs in rats. Eur. J. Endocrinol. 152:887-894. crossref(new window)

Silverman, B. L., M. Bettendorf, S. L. Kaplan, M. M. Grumbach and W. L. Miller. 1989. Regulation of growth hormone (GH) secretion by GH-releasing factor, somatostatin, and insulingrowth factor I in ovine fetal and neonatal pituitary cells in vitro. Endocrinol. 124:84-89. crossref(new window)

Simmen, F. A., L. Badinga, M. L. Green, I. Kwak, S. Song and C. M. Simmen. 1998. The porcine insulin-like growth factor system: at the interface of nutrition, growth and reproduction. J. Nutr. 128:315S-320S. crossref(new window)

Smith, R. G., K. Cheng, W. R. Schoen, S. S. Pong, G. Hickey, T. Jacks, B. Butler, W. W. Chan, L. Y. P. Chaung, F. Judith, J. Taylor, M. J. Wyvratt and M. H. Fisher. 1993. A nonpeptidyl growth hormone secretagogue. Sci. 260:1640-1643. crossref(new window)

Stanley, S., K. Wynne, B. McGowan and S. Bloom. 2005. Hormonal regulation of food intake. Physiol. Rev. 85:1131-1158. crossref(new window)

Stewart, J. K., D. J. Koerker and C. J. Goodner. 1984. Effects of branched chain amino acids on spontaneous growth hormone secretion in the baboon. Endocrinol. 115:1897-1900. crossref(new window)

Sticker, L. S., D. L. Thompson, J. M. Fernandez, L. D. Bunting and C. L. DePew. 1995. Dietary protein and (or) energy restriction in mares: plasma growth hormone, IGF-I, prolactin, cortisol, and thyroid hormone responses to feeding, glucose, and epinephrine. J. Anim. Sci. 73:1424-1432. crossref(new window)

Sticker, L. S., D. L. Thompson and L. R. Gentry. 2001. Pituitary hormone and insulin responses to infusion of amino acids and N-methyl-D, L-aspartate in horses. J. Anim. Sci. 79:735-744. crossref(new window)

Sturm, K., C. G. MacIntosh, B. A. Parker, J. Wishart, M. Horowitz and I. M. Chapman. 2003. Appetite, food intake, and plasma concentrations of cholecystokinin, ghrelin, and other gastrointestinal hormones in undernourished older women and well-nourished young and older women. J. Clin. Endocrinol. Metab. 88:3747-3755. crossref(new window)

Sugino, T., Y. Hasegawa, Y. Kurose, M. Kojima, K. Kangawa and Y. Terashima. 2004. Effects of ghrelin on food intake and neuroendocrine function in sheep. Anim. Reprod. Sci. 82/83:183-194. crossref(new window)

Takaya, K., H. Ariyasu, N. Kanamoto, H. Iwakura, A. Yoshimoto, M. Harada, K. Mori, Y. Komatsu, T. Usui, A. Shimatsu, Y. Ogawa, K. Hosoda, T. Akamizu, M. Kojima, K. Kangawa and K. Nakao. 2000. Ghrelin strongly stimulates growth hormone release in humans. J. Clin. Endocrinol. Metabol. 85:4908-4911. crossref(new window)

Tannenbaum, G. S., J. B. Martin and E. Colle. 1976. Ultradian growth hormone rhythm in the rat: effects of feeding, hyperglycemia, and insulin-induced hypoglycemia. Endocrinol. 99:720-727. crossref(new window)