Laboratorio de Investigaciones Fisiológicas Experimentales, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Santa Fe, Argentina.
J Inorg Biochem. 2009 Nov;103(11):1542-7. doi: 10.1016/j.jinorgbio.2009.07.017. Epub 2009 Aug 14.
To analyse the influence of thyroid status on the effect of aluminium (Al) upon intestinal calcium (Ca) absorption, adult male Wistar rats with experimentally altered thyroid hormones circulating levels, were orally treated (o.g.) with 0 (control), or 50 mg elemental Al (as chloride)/kg body weight (b.w.) per day, for a 14 d period. Hyper- and hypo-thyroid conditions were respectively achieved by means of administration of either sodium levothyroxine (50 microg/kg b.w. per day, o.g.) or methimazole, a thyroxine synthesis inhibitor (1mg/kg b.w. per day, o.g.). In duodenum-jejunum segments, in vitro mucosa-to-serosa (45)Ca flux (JCa(ms)) and kinetics of (45)Ca uptake in isolated enterocytes, were determined. In serum, concentrations of thyroxine (T4) and triiodothyronine (T3) were measured by chemiluminescent enzyme immunoassay. Unlike non-Al-treated rats, JCa(ms) of Al-exposed rats decreased as serum levels of T4 and T3 increased, showing a significant inverse correlation in both cases (T4: r(2)=0.414, P=0.024; T3: r(2)=0.443, P=0.018). Enterocytes isolated from rats treated with Al plus thyroxine showed a reduction of both maximum Ca uptake (4.86+/-0.44 vs. 6.85+/-1.04 nmol Ca/mg protein, P<0.05) and K(m) (0.84+/-0.18 vs. 1.05+/-0.36 mM, P<0.05) when compared to control. The observed variability in the Al effect on Ca transport with thyroid status of rats could be reflecting a negative interaction of Al with thyroid hormone action mechanisms on intestinal Ca absorption, which would take place mainly at Ca entry into enterocyte from lumen.
为了分析甲状腺状态对铝（Al）影响肠道钙（Ca）吸收的影响，实验改变了甲状腺激素循环水平的成年雄性 Wistar 大鼠，经口给予 0（对照）或 50mg 元素 Al（作为氯化物）/kg 体重（b.w.）/天，为期 14 天。分别通过给予左甲状腺素钠（50μg/kg b.w. /天，经口）或甲状腺素合成抑制剂甲巯咪唑（1mg/kg b.w. /天，经口）来实现甲状腺功能亢进和甲状腺功能减退状态。在十二指肠-空肠段，测定体外黏膜-浆膜（45）Ca 通量（JCa（ms））和分离肠细胞中（45）Ca 摄取的动力学。在血清中，通过化学发光酶免疫分析法测定甲状腺素（T4）和三碘甲状腺原氨酸（T3）的浓度。与未接受 Al 治疗的大鼠不同，暴露于 Al 的大鼠的 JCa（ms）随着血清 T4 和 T3 水平的升高而降低，在两种情况下均显示出显著的负相关（T4：r（2）=0.414，P=0.024；T3：r（2）=0.443，P=0.018）。用 Al 加甲状腺素治疗的大鼠分离的肠细胞显示最大 Ca 摄取（4.86+/-0.44 与 6.85+/-1.04 nmol Ca/mg 蛋白，P<0.05）和 K（m）（0.84+/-0.18 与 1.05+/-0.36 mM，P<0.05）均降低。与大鼠甲状腺状态的大鼠 Al 对 Ca 转运的影响的可变性可能反映了 Al 与甲状腺激素作用机制对肠道 Ca 吸收的负相互作用，这主要发生在 Ca 从腔进入肠细胞的过程中。
