Wajner Simone Magagnin, dos Santos Wagner Márcia, Melo Rossana C N, Parreira Gleydes G, Chiarini-Garcia Hélio, Bianco Antonio C, Fekete Csaba, Sanchez Edith, Lechan Ronald M, Maia Ana Luiza
Endocrine Division, Thyroid Section, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
J Endocrinol. 2007 Jul;194(1):47-54. doi: 10.1677/JOE-07-0106.
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.
传统上，睾丸被描述为对甲状腺激素无反应的组织，但最近的研究表明，这些激素可能在睾丸发育中发挥重要作用。我们之前已经证明，2型碘甲状腺原氨酸脱碘酶（D2），一种甲状腺激素激活酶，在成年啮齿动物睾丸中表达，并且其活性由甲状腺功能减退诱导。然而，D2在睾丸中的精确位置尚不清楚。本研究的目的是使用实时PCR分析、原位杂交组织化学以及测定从成年甲状腺功能正常和/或甲状腺功能减退大鼠睾丸分离的细胞组分中的D2活性，来确定表达D2的睾丸细胞类型。生殖细胞中的D2 mRNA水平高于体细胞（6.94±1.49对2.32±0.79任意单位（au）；P = 0.017）。甲状腺功能减退增加了生殖细胞中D2的表达（6.94±1.49对8.78±5.43 au，P = 0.002），但未显著改变体细胞中的D2转录本（2.12±0.79对2.88±1.39 au，P = 0.50）。原位杂交分析表明，D2 mRNA特异性存在于正在分化的延长型精子细胞中，而其他生殖细胞类型、生精上皮的支持细胞和间质细胞对此酶几乎呈阴性。在生殖细胞和体细胞分离的细胞组分中测得的酶活性（分别为0.23±0.003对0.02±0.013 fmol/分钟每毫克蛋白质；P < 0.001）进一步证实了实时PCR和原位杂交结果。因此，我们的研究结果表明，D2主要在延长型精子细胞中表达，提示甲状腺激素可能对成年大鼠的精子发生有直接影响。
