This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Schomburg, L. Articles by Bauer, K. Search for Related Content PubMed PubMed Citation Articles by Schomburg, L. Articles by Bauer, K.

Regulation of the Adenohypophyseal Thyrotropin-Releasing Hormone-Degrading Ectoenzyme by Estradiol¹

Max-Planck-Institut für experimentelle Endokrinologie, 30603 Hannover, Germany

Address all correspondence and requests for reprints to: Dr. Karl Bauer, Max-Planck-Institut für experimentelle Endokrinologie, POB 610309, 30603 Hannover, Germany. E-mail: 106001,2503{at}compuserve.com

TRH is inactivated by the TRH-degrading ectoenzyme, a TRH-specific metallopeptidase. At the pituitary level, this enzyme is stringently regulated by thyroid hormones. We describe here gender-related differences and the effect of estradiol (E₂) on the expression of this enzyme in the anterior pituitary.

Compared with male rats, only about one third of the enzymatic activities and the messenger RNA levels were found in the anterior pituitary of female rats, whereas the TRH receptor transcript levels were found inversely related. When male rats received a single injection of 0.5 µg E₂/100 g BW, the enzymatic activity decreased to 65% of control values within 14 h, preceded by a decrease of the transcript levels to 25% of control within 6 h. Basal values were reached again 24–48 h after the injection. E₂ had no effect on the expression of the enzyme in the brain. In vivo and with GH₃ cells in vitro, E₂ effectively counteracted the increase in enzymatic activity induced by T₃, whereas neither testosterone nor progesterone, aldosterone, or dexamethasone showed any significant effects.

Because the expression of the adenohypophyseal TRH-degrading ectoenzyme is tightly regulated by both T₃ and E₂ with adequate dynamics, we conclude that this peptidase serves integrative functions for the control of TRH-stimulated hormone secretion.

This article has been cited by other articles:

				D. Desaulniers, K. Leingartner, B. Musicki, A. Yagminas, G.-H. Xiao, J. Cole, L. Marro, M. Charbonneau, and B. K. Tsang Effects of Postnatal Exposure to Mixtures of Non-ortho-PCBs, PCDDs, and PCDFs in Prepubertal Female Rats Toxicol. Sci., October 1, 2003; 75(2): 468 - 480. [Abstract] [Full Text] [PDF]

				J. Ehrchen, A. Peters, D. K. Lüdecke, T. Visser, and K. Bauer Analysis of Thyrotropin-Releasing Hormone-Signaling Components in Pituitary Adenomas of Patients with Acromegaly J. Clin. Endocrinol. Metab., August 1, 2000; 85(8): 2709 - 2713. [Abstract] [Full Text]

				D. F. Carmignac, P. A. Bennett, and I. C. A. F. Robinson Effects of Growth Hormone Secretagogues on Prolactin Release in Anesthetized Dwarf (dw/dw) Rats Endocrinology, August 1, 1998; 139(8): 3590 - 3596. [Abstract] [Full Text] [PDF]