Galanin gene expression in radiothyroidectomy-induced thyrotroph
adenomas.
Hyde, James F., Joseph P. Moore, Jr., Karen W. Drake, and David G.
Morrison.
Department of Anatomy and Neurobiology, University of Kentucky
College of Medicine, Lexington, Kentucky 40536
APStracts 3:0048E, 1996.
Galanin gene expression is markedly increased in the anterior
pituitary glands of estrogen-treated rats (lactotroph hyperplasia),
as well as human growth hormone-releasing hormone transgenic mice
(somatotroph hyperplasia). The objective of this study was to examine
galanin in a mouse model of thyrotroph adenoma formation. Male mice
were radio-thyroidectomized using iodine-131 (I-131), and galanin
peptide levels were assessed in the hypothalamic-pituitary axis.
Immunoreactive galanin concentrations in the anterior pituitaries of
I-131-treated mice were decreased 80% at 3, 6, 9 and 12 months after
radiothyroidectomy. Galanin peptide levels in the hypothalamus were
decreased 20-25% at these times. Treatment with either estradiol or
3,3'-5-triiodo-L-thyronine increased galanin peptide concentrations
in the anterior pituitaries of I-131-treated mice, but neither
treatment restored galanin concentrations. Galanin mRNA levels were
decreased more than 80% one year after radiothyroidectomy. We
conclude that unlike animal models of lactotroph and somatotroph
hyperplasia, galanin gene expression is suppressed throughout the
development of thyrotroph adenomas, suggesting that galanin does not
have a stimulatory role in the proliferation of thyrotrophs.
Moreover, these data show that thyroid hormones are important
positive regulators of galanin gene expression in the mouse, and that
estrogen may stimulate galanin gene expression in the absence of
thyroid hormones.
Received 9 November 1995; accepted in final form 15 February
1996.
APS Manuscript Number E529-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96