Diurnal Change of Thyroid‐Stimulating Hormone mRNA Expression in the Rat Pars Tuberalis

Journal of Neuroendocrinology - Tập 19 Số 11 - Trang 839-846 - 2007
Sayaka Aizawa1, Satoya Hoshino1, Ichiro Sakata1, Akio Adachi1, Sayaka Yashima2, Atsuhiko Hattori2, Tatsuo Sakai1
1Graduate School of Science and Engineering Division of Life Science, Area of Regulatory Biology, Saitama University, Saitama, Japan.
2Department of Biology, College of Liberal Arts and Sciences, Tokyo Medical and Dental University, Chiba, Japan

Tóm tắt

Thyroid‐stimulating hormone (TSH)‐producing cells (TSH cells), which account for a large fraction of the cells in the rat pars tuberalis (PT), have been found to express MT1 melatonin receptor and mammalian clock genes at high densities. Although these findings suggest that TSH production in the rat PT is regulated by melatonin and/or the biological clock, there have been no studies focusing on the diurnal change and regulation mechanism of TSH production in the rat PT. Therefore, in the present study, we examined diurnal changes of in TSHβ and α‐glycoprotein subunit (αGSU) mRNA expression and TSH immunoreactivity (‐ir) in the rat PT, and also examined the relationship between melatonin and TSH production in vivo. Both TSHβ mRNA expression and αGSU mRNA expression in the PT showed diurnal variations: the expression levels were lowest at the light phase [Zeitgeber time (ZT)4] and high at the dark phase (ZT12 and ZT20). TSH‐ir in the PT showed the lowest level at ZT4, as was found for mRNA expression. Interestingly, TSH‐ir, which was confined to the Golgi apparatus at ZT4, spread to the cytoplasm, and most of the TSH cells in the PT were uniformly immunostained in the cytoplasm at ZT20. Despite the fact that chronic administration of melatonin suppressed TSHβ and αGSU mRNA expression, TSH‐ir in the PT was significantly enhanced. These findings results clearly show that there are diurnal changes in TSH expression and accumulation in rat PT‐TSH cells and suggest that these fluctuations are regulated by melatonin.

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Thông tin xuất bản

Journal of Neuroendocrinology

Tập 19 Số 11

839-846

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