Dulhunty A F, Gage P W, Lamb G D
J Muscle Res Cell Motil. 1986 Jun;7(3):225-36. doi: 10.1007/BF01753555.
Isometric twitches, passive electrical properties and the amounts of transverse (T) tubule system and terminal cisternae in extensor digitorum longus (EDL) and soleus muscle fibres were measured in normal rats and rats given daily injections of triiodothyronine (T3, 150 micrograms kg-1) for 15-25 days. Isometric twitches in both muscles were more rapid after the T3-treatment, particularly in soleus. Cable properties were measured using a three-microelectrode, end-of-fibre, voltage clamp technique. In order to increase the space constant of the T-tubule system, extracellular solutions were used that reduced ionic, particularly chloride, conductance. Fibre diameter was less than normal in the hyperthyroid rats. Membrane capacity, per cm2 of fibre surface, increased in both EDL and soleus muscles and there was a decrease in membrane resistance. The volume and surface area of the T-system and terminal cisternae were measured using standard morphometric techniques. Following T3-treatment the amount of T-tubule system per 100 micron3 of fibre volume, in both EDL and soleus fibres, was twofold higher than in normal fibres. The larger area of T-tubule membrane per unit volume was sufficient to account for the increase in membrane capacity. In contrast, the amount of terminal cisternae per 100 micron3 of fibre was unchanged in EDL following T3-treatment and there was only a small increase in soleus. As a consequence, the normal relationship between the T-tubules and terminal cisternae was changed in both muscles. There was an increase in the numbers of 'bare' T-tubules and an increased occurrence of diadic, pentadic and heptadic junctions between the membranes of the T-tubules and terminal cisternae. The results suggest that thyroid hormone has a differential effect on the synthesis of T-tubule and terminal cisternae membrane, resulting in a disproportionately large amount of T-tubule membrane.
在正常大鼠以及每日注射三碘甲状腺原氨酸（T3，150微克/千克）15 - 25天的大鼠中，测量了趾长伸肌（EDL）和比目鱼肌纤维的等长收缩、被动电特性以及横管（T）系统和终池的数量。T3处理后，两块肌肉的等长收缩都加快，尤其是比目鱼肌。使用三微电极、纤维末端电压钳技术测量电缆特性。为了增加T管系统的空间常数，使用了降低离子尤其是氯离子电导的细胞外溶液。甲状腺功能亢进大鼠的纤维直径小于正常水平。每平方厘米纤维表面的膜电容在EDL和比目鱼肌中均增加，膜电阻降低。使用标准形态计量学技术测量T系统和终池的体积和表面积。T3处理后，EDL和比目鱼肌纤维每100立方微米纤维体积中的T管系统数量比正常纤维高两倍。单位体积内较大的T管膜面积足以解释膜电容的增加。相比之下，T3处理后EDL中每100立方微米纤维的终池数量未变，比目鱼肌中仅略有增加。因此，两块肌肉中T管和终池之间的正常关系发生了变化。“裸露”T管数量增加，T管膜与终池膜之间二联体、五联体和七联体连接的发生率增加。结果表明，甲状腺激素对T管和终池膜的合成有不同影响，导致T管膜数量不成比例地大量增加。
