Segal J
Charles A. Dana Research Institute, Boston, Massachusetts.
Biochemistry. 1988 Apr 5;27(7):2586-90. doi: 10.1021/bi00407a047.
3,5,3'-Triiodothyronine (T3) produced a rapid and transient increase in 45Ca uptake and cytoplasmic free calcium concentration in rat thymocytes, which is the most rapid effect of T3 in this system. This effect was manifested in cells suspended in medium containing 1 mM calcium. The T3 effect on 45Ca uptake was evident at 15-30 s, reached maximum at 30-60 s, and returned to control values at 5 min. The T3 effect on cytoplasmic free calcium concentration was seen after 30 s, reached maximum at 7 min, and returned to control values after 24 min. In cells suspended in Ca2+-free medium, T3 produced a similar rapid increase in 45Ca uptake, which was sustained for at least 60 min, but T3 failed to change cytoplasmic free calcium concentration. Alprenolol (10 microM) blocked the stimulatory effects of T3 on these two functions in a similar fashion. From these results, I suggest that in rat thymocytes T3 influences cellular calcium economy through a biphasic mechanism in which T3 first increases calcium uptake which, in turn, is followed by a release of calcium from intracellular pool(s), resulting in a further increase in cytoplasmic free calcium concentration and the activation of Ca2+ -regulated systems. Moreover, the present study provides further support for the postulate that in the rat thymocyte calcium serves as the first messenger for the plasma membrane-mediated stimulatory effects of T3 on several metabolic functions.
3,5,3'-三碘甲状腺原氨酸（T3）可使大鼠胸腺细胞对45Ca的摄取及细胞质游离钙浓度迅速短暂升高，这是T3在此系统中最快速的效应。此效应在悬浮于含1 mM钙的培养基中的细胞中表现明显。T3对45Ca摄取的效应在15 - 30秒时明显，在30 - 60秒时达到最大值，并在5分钟时恢复到对照值。T3对细胞质游离钙浓度的效应在30秒后可见，在7分钟时达到最大值，并在24分钟后恢复到对照值。在悬浮于无钙培养基中的细胞中，T3使45Ca摄取同样迅速增加，并持续至少60分钟，但T3未能改变细胞质游离钙浓度。阿普洛尔（10 microM）以类似方式阻断了T3对这两种功能的刺激作用。从这些结果来看，我认为在大鼠胸腺细胞中，T3通过双相机制影响细胞钙代谢，其中T3首先增加钙摄取，进而导致钙从细胞内钙库释放，从而使细胞质游离钙浓度进一步升高并激活Ca2+调节系统。此外，本研究进一步支持了以下假设：在大鼠胸腺细胞中，钙作为T3对几种代谢功能的质膜介导刺激效应的第一信使。
