Departamento de Genética y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México.
J Neuroendocrinol. 2009 May;21(5):439-48. doi: 10.1111/j.1365-2826.2009.01861.x.
Energy expenditure and thermogenesis are regultated by thyroid and sex hormones. Several parameters of hypothalamic-pituitary-thyroid (HPT) axis function are modulated by 17β-oestradiol (E(2)) but its effects on thyrotrophin-releasing hormone (TRH) mRNA levels remain unknown. We evaluated, by in situ hybridisation and Northern bloting, TRH expression in the paraventricular nucleus of the hypothalamus (PVN) of cycling rats, 2 weeks-ovariectomised (OVX) and OVX animals injected s.c. during 1-4 days with E(2) (5, 50, 100 or 200 μg ⁄ kg) (OVX-E). Serum levels of E(2), thyroid-stimulating hormone (TSH), prolactin, corticosterone and triiodothyronine (T(3)) were quantified by radioimmunoassay. Increased serum E(2) levels were observed after 4 days injection of 50 μg ⁄ kg E(2) (to 68.5 ± 4.8 pg ⁄ ml) in OVX rats. PVN-TRH mRNA levels were slightly higher in OVX than in virgin females at dioestrous 1 or pro-oestrous, decreasing proportionally to increased serum E(2) levels. E(2) injections augmented serum T(3), prolactin, and corticosterone levels. Serum TSH levels augmented with 4 days 50 μg ⁄ kg E(2), but not with the higher doses that enhanced serum T(3) levels. Exposure to cold for 1 h resulted in marked HPT axis activation in OVX rats, increasing the levels of TRH mRNA along the rostro-caudal PVN areas, as well as serum TSH, T(3), corticosterone and prolactin levels. By contrast, no significant changes in any of these parameters were observed in cold-exposed OVX-E (50 μg ⁄ kg E(2)) rats. Very few PVN-TRHergic neurones expressed the oestrogen receptor type-α, suggesting that the effects of E(2) on PVN-TRH expression are indirect, most probably as a result of its multiple modulatory effects on circulating hormones and their receptor sensitivity. The blunted response of OVX-E rats to cold coincides with the effects of E(2) on the autonomic nervous system and increased cold tolerance.
能量消耗和产热受甲状腺和性激素调节。几种下丘脑-垂体-甲状腺（HPT）轴功能的参数受 17β-雌二醇（E2）调节，但它对促甲状腺素释放激素（TRH）mRNA 水平的影响尚不清楚。我们通过原位杂交和 Northern blot 评估了发情周期大鼠、2 周卵巢切除（OVX）大鼠和皮下注射 E2（5、50、100 或 200μg/kg）（OVX-E）1-4 天的下丘脑室旁核（PVN）中的 TRH 表达。用放射免疫法测定血清 E2、促甲状腺激素（TSH）、催乳素、皮质酮和三碘甲状腺原氨酸（T3）水平。OVX 大鼠注射 50μg/kg E2 4 天后，血清 E2 水平升高（至 68.5±4.8pg/ml）。OVX 大鼠发情期 1 天或发情前期的 PVN-TRH mRNA 水平略高于未交配的雌性，且与血清 E2 水平成正比。E2 注射增加了血清 T3、催乳素和皮质酮水平。血清 TSH 水平随着 4 天 50μg/kg E2 的注射而升高，但随着血清 T3 水平升高的较高剂量则不会升高。暴露于寒冷 1 小时会导致 OVX 大鼠 HPT 轴明显激活，增加沿 PVN 区的 TRH mRNA 水平，以及血清 TSH、T3、皮质酮和催乳素水平。相比之下，暴露于寒冷的 OVX-E（50μg/kg E2）大鼠中，这些参数没有明显变化。很少有 PVN-TRH 能神经元表达雌激素受体-α，这表明 E2 对 PVN-TRH 表达的影响是间接的，很可能是由于其对循环激素及其受体敏感性的多种调节作用。OVX-E 大鼠对寒冷的反应迟钝与 E2 对自主神经系统的影响和增加的耐寒性相吻合。
