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Title: THE CONTROL OF ADENOHYPOPHYSIAL HORMONE SECRETION BY AMINO ACIDS AND PEPTIDES IN SWINE

Author
item ESTIENNE, MARK - VIRGINIA POLYTECHNIC INST
item Barb, Claude

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2004
Publication Date: 7/20/2005
Citation: Estienne, M.J., Barb, C.R. 2005. The control of adenohypophysial hormone secretion by amino acids and peptides in swine. Domestic Animal Endocrinology. 29:34-42.

Interpretive Summary: Understanding the mechanisms that regulate growth hormone (GH) secretion, necessary for stimulation of growth, and luteinizing hormone (LH) , necessary for reproduction, is of great relevance during pubertal development in the pig. Evidence supports the idea that brain hormones regulate LH and GH secretion by acting directly on the pituitary gland. Thus, understanding these interactions is necessary in order to develop new methods to promote maximal growth and enhance reproductive function in the pig.

Technical Abstract: In swine, the most extensively studied modulators of adenohypophysial hormone secretion are the excitatory amino acids (ExAA), namely glutamate and aspartate, and the endogenous opioid peptides (EOP). In general, excitatory amino acids stimulate release of luteinizing hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH), and prolactin (PRL). Secretion of adenohypophysial hormones induced by ExAA is primarily, but perhaps not exclusively, a consequence of action at the central nervous system. By acting primarily at the level of the central nervous system, EOP inhibit LH secretion, stimulate GH release and depending on the animal model studied, exert either stimulatory or inhibitory influences on PRL secretion. However, the EOP also inhibited LH release by direct action on the adenohypophysis. More recently, peptides such as neuropeptide-Y (NPY), orexin-B, ghrelin, galanin, and substance P have been evaluated for possible roles in controlling adenohypophysial hormone secretion in swine. For example, NPY, orexin-B, and ghrelin increased basal GH secretion and modulated the GH response to GHRH, at least in part, by direct action on the adenohypophysis. Secretion of LH was stimulated by orexin-B, galanin and substance P from porcine pituitary cells in vitro. Because the ExAA and various peptides modulate secretion of adenohypophysial hormones, these compounds may play an important role in regulating swine growth and reproduction.