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Experimental Biology and Medicine 231:1610-1615 (2006)
© 2006 Society for Experimental Biology and Medicine

ORIGINAL RESEARCH ARTICLE

A BRIEF COMMUNICATION

Central Effects of Ghrelin on Serum Growth Hormone and Morphology of Pituitary Somatotropes in Rats

D. Stevanovic*,1, V. Milosevic{dagger}, D. Nesic*, V. Ajdzanovic{dagger}, V. Starcevic* and W. B. Severs{ddagger}

* Institute of Physiology School of Medicine, University of Belgrade, Belgrade, Serbia; {dagger} Institute for Biological Research "Sinis a Stankovic," Belgrade, Serbia; and {ddagger} Department of Pharmacology, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania 17033

To whom requests for reprints should be addressed at 1 Institute of Physiology School of Medicine, University of Belgrade, Vis egradska 26/II, Belgrade 11001, Serbia. E-mail: sted{at}eunet.yu

Ghrelin, an endogenous ligand for the growth hormone (GH) secretagogue receptor, was originally purified from rat stomach; subsequently, ghrelin neurons were found in the arcuate nuclei of rats. Central effects of the peptide on GH release, however, remain to be clarified. The aim of the present study was to determine the morphologic features of GH-producing pituicytes and serum GH concentration after central administration of ghrelin. Five injections of rat ghrelin or phosphate-buffered saline (PBS; n = 10 rats/group) were given every 24 hrs (1 µg of ghrelin in 5 µl of PBS) into the lateral cerebral ventricle of male rats. Significant (P < 0.05) increases in absolute and relative pituitary weights occurred in ghrelin-treated rats versus controls (58% and 41%, respectively). Morphometric parameters (i.e., the volume of GH cells, volume of their nuclei, and volume density) all significantly (P < 0.05) increased by 17%, 18%, and 19%, respectively, in the ghrelin-treated group versus controls. Terminal serum concentration of GH was significantly (P < 0.05) increased by 15% with ghrelin treatment. The results clearly document that daily nanomolar doses of ghrelin into the lateral cerebral ventricle stimulate GH cell proliferation and promote GH release. Thus, achieving pharmacologic control of central ghrelin receptors is a promising modality to modulate the actions of GH.

Key Words: ghrelin • cerebroventricular injections • pituitary • GH cells • rats • morphology






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