Role of leptin in modulating the hypothalamic–pituitary axis and luteinizing hormone secretion in the prepuberal gilt

Three experiments (EXP) were conducted to test the hypothesis that leptin modulates LH, GnRH, and neuropeptide Y (NPY) secretion. In EXP I, prepuberal gilts received intracerebroventricular (i.c.v.) leptin injections and blood samples were collected. In EXP II, anterior pituitary cells from prepuber...

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Bibliographic Details
Published in:	Domestic animal endocrinology Vol. 26; no. 3; pp. 201 - 214
Main Authors:	Barb, C.R, Barrett, J.B, Kraeling, R.R
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 01-04-2004
Subjects:	Animals anterior pituitary dose response Estradiol - blood Female gilts gonadotropin release Gonadotropin-releasing hormone Gonadotropin-Releasing Hormone - metabolism Gonadotropin-Releasing Hormone - secretion hormonal regulation hormone secretion Hypothalamo-Hypophyseal System - drug effects Hypothalamo-Hypophyseal System - physiology hypothalamus Hypothalamus - metabolism In Vitro Techniques Leptin Leptin - pharmacology Leptin - physiology Luteinizing hormone Luteinizing Hormone - blood Luteinizing Hormone - metabolism Luteinizing Hormone - secretion neuropeptide Y Neuropeptide Y - metabolism Neuropeptide Y - secretion Pig Pituitary Gland, Anterior - metabolism Pituitary Gland, Anterior - secretion Pituitary-Adrenal System - drug effects Pituitary-Adrenal System - physiology preoptic area Progesterone - blood swine Swine - physiology Luteinizing hormone Gonadotropin-releasing hormone Leptin Pig
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Summary:	Three experiments (EXP) were conducted to test the hypothesis that leptin modulates LH, GnRH, and neuropeptide Y (NPY) secretion. In EXP I, prepuberal gilts received intracerebroventricular (i.c.v.) leptin injections and blood samples were collected. In EXP II, anterior pituitary cells from prepuberal gilts in primary culture were challenged with 10 −14, 10 −13, 10 −12, 10 −11, 10 −10, 10 −9, 10 −8, 10 −7, or 10 −6 M leptin individually or in combinations with 10 −10, 10 −9, and 10 −8 M GnRH. In EXP III, hypothalamic–preoptic area (HYP-POA) explants were placed in perfusion system and exposed to 0 ( n=5), 10 −12 M ( n=4), 10 −10 M ( n=4), 10 −8 M ( n=4), or 10 −6 M ( n=5) human recombinant leptin (LEP) for 30 min. In EXP I, serum LH concentrations were unaffected by leptin treatment. In EXP II, all doses of leptin increased LH secretion except for 10 −12 and 10 −7 M. Only 10 −7, or 10 −13 M leptin in combination with 10 −8 or 10 −9 M GnRH, respectively, suppressed LH secretion. In EXP III, prior to leptin, media GnRH concentrations were similar across treatments. Media GnRH concentrations increased after 10 −12, 10 −10, and 10 −8 M leptin compared to control. Leptin treatment failed to influence NPY secretion across treatments. These results indicate that components of the neuroendocrine axis that regulate GnRH and LH secretion are functional and leptin sensitive before the onset of puberty. Other neural peptides in addition to NPY may mediate the acute effects of leptin on the GnRH-LH system and lastly, the inability of i.c.v. leptin treatment to increase LH secretion may in part be related to stage of sexual maturation and associated change in negative feedback action of estradiol on LH secretion.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0739-7240 1879-0054
DOI:	10.1016/j.domaniend.2003.10.004