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Anterior Pituitary Leptin Expression Changes in Different Reproductive States: In Vitro Stimulation by Gonadotropin-releasing Hormone

Noor Akhter, Brandy W. Johnson, Christopher Crane, Mary Iruthayanathan, Yi-Hong Zhou, Akihiko Kudo and Gwen V. Childs

Department of Neurobiology and Developmental Sciences, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas (NA,BWJ,CC,GVC); Division of Endocrinology, Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa (MI); Department of Neurological Surgery, University of California Irvine, Orange, California (Y-HZ); and Department of Anatomy, Kyorin University School of Medicine, Tokyo, Japan (AK)

Correspondence to: Noor Akhter, PhD, Department of Neurobiology and Developmental Sciences, College of Medicine, University of Arkansas for Medical Sciences, 4301 W. Markham St., Slot 510, Little Rock, AR 72205. E-mail: akhternoor{at}uams.edu

This study was designed to learn more about the changes in expression of rat anterior pituitary (AP) leptin during the estrous cycle. QRT-PCR assays of cycling rat AP leptin mRNA showed 2-fold increases from metestrus to diestrus followed by an 86% decrease on the morning of proestrus. Percentages of leptin cells increased in proestrus and pregnancy to 55–60% of AP cells. Dual labeling for leptin proteins and growth hormone (GH) or gonadotropins showed that the rise in leptin protein-bearing cells from diestrus to proestrus was mainly in GH cells. Only 10–20% of leptin cells in male or cycling female rats coexpress gonadotropins. In contrast, 50–73% of leptin cells from pregnant or lactating females coexpress gonadotropins and only 19% coexpress GH, indicating plasticity in the distribution of leptin. Leptin cells expressed GnRH receptors, and estrogen and GnRH together increased the coexpression of leptin mRNA and gonadotropins. GnRH increased cellular leptin proteins three to four times and mRNA 9.8 times in proestrous rats and stimulated leptin secretion in cultures from diestrous, proestrous, and pregnant rats. These regulatory influences, and the high expression of AP leptin during proestrus and pregnancy, suggest a supportive role for leptin during key events involved with reproduction. (J Histochem Cytochem 55:151–166, 2007)

Key Words: leptin • gonadotropes • somatotropes • gonadotropin-releasing hormone • estrous cycle • pregnancy • lactation • QRT-PCR • in situ hybridization • immunolabeling

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				C. Crane, N. Akhter, B. W. Johnson, M. Iruthayanathan, F. Syed, A. Kudo, Y.-H. Zhou, and G. V. Childs Fasting and Glucose Effects on Pituitary Leptin Expression: Is Leptin a Local Signal for Nutrient Status? J. Histochem. Cytochem., October 1, 2007; 55(10): 1059 - 1073. [Abstract] [Full Text] [PDF]

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