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Endocrine Division, Thyroid Section, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
1 Laboratory of Cellular Biology, Department of Biology, Universidade Federal de Juiz de Fora, Juiz de Fora, Minas Gerais, Brazil
2 Laboratory of Structural Biology and Reproduction, Department of Morphology, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
3 Division of Endocrinology, Diabetes and Hypertension, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
4 Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest H-1083, Hungary
5 Division of Endocrinology, Diabetes, and Metabolism, Tufts-New England Medical Center, Boston, Massachusetts, USA
(Requests for offprints should be addressed to A L Maia who is now at Setor de Tireóide, Serviço de Endocrinologia, Hospital de Clínicas de Porto Alegre, Rua Ramiro Barcelos, 2350, 90035-003 Porto Alegre, Rio Grande do Sul, Brazil; Email: almaia{at}ufrgs.br)
* (S M Wajner and M dos Santos Wagner contributed equally to this study) The testis has been classically described as a thyroid hormone unresponsive tissue, but recent studies indicate that these hormones might play an important role in developing testes. We have previously demonstrated that type 2 iodothyronine deiodinase (D2), a thyroid hormone-activating enzyme, is expressed in adult rodent testis and that its activity is induced by hypothyroidism. Nevertheless, the precise location of D2 in testis is not known. The aim of the present work was to determine the testicular cell types in which D2 is expressed using real-time PCR analysis, in situ hybridization histochemistry, and determination of D2 activity in cell fractions isolated from adult euthyroid and/or hypothyroid rat testis. The D2 mRNA levels in germ cells were higher than those from somatic cells (6.94 ± 1.49 vs 2.32 ± 0.79 arbitrary units (au); P = 0.017). Hypothyroidism increased D2 expression in germ cells (6.94 ± 1.49 vs 8.78 ± 5.43 au, P = 0.002) but did not change D2 transcripts in somatic cells significantly (2.12 ± 0.79 vs 2.88 ± 1.39 au, P = 0.50). In situ hybridization analysis showed that D2 mRNA is specifically present in elongated spermatids undergoing differentiation, whereas other germ cell types and Sertoli cells of seminiferous epithelium and the interstitial cells were virtually negative for this enzyme. The enzyme activity measured in germ and somatic isolated cell fractions (0.23 ± 0.003 vs 0.02 ± 0.013 fmol/min per mg protein respectively; P < 0.001) further confirmed the real-time PCR and in situ hybridization results. Hence, our findings demonstrated that D2 is predominantly expressed in elongated spermatids, suggesting that thyroid hormone might have a direct effect on spermatogenesis in the adult rats.
This article has been cited by other articles:
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  M. S. Wagner, S. M. Wajner, and A. L. Maia The role of thyroid hormone in testicular development and function J. Endocrinol., December 1, 2008; 199(3): 351 - 365. [Abstract] [Full Text] [PDF]
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 B. Anguiano, N. Aranda, G. Delgado, and C. Aceves Epididymis Expresses the Highest 5'-Deiodinase Activity in the Male Reproductive System: Kinetic Characterization, Distribution, and Hormonal Regulation Endocrinology, August 1, 2008; 149(8): 4209 - 4217. [Abstract] [Full Text] [PDF]
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