Sayen M R, Rohrer D K, Dillmann W H
Department of Medicine, University of California, San Diego 92103.
Mol Cell Endocrinol. 1992 Sep;87(1-3):87-93. doi: 10.1016/0303-7207(92)90236-y.
The thyroid status markedly influences the contractile function of muscle, and changes in the activity of the Ca2+ ATPase of the sarcoplasmic reticulum (SR) contribute to these alterations. Two separate genes encode the major isoforms of SR Ca2+ ATPase. In fast skeletal muscle, sarcoplasmic endoplasmic reticulum Ca2+ ATPase type 1 (SERCa1) presents the major isoform, whereas in slow skeletal muscle SERCa type 2 (SERCa2) predominates. Cardiac muscle contains only SERCa2. To examine the mechanisms responsible for changes in contractile function, we quantitated SERCa1 and SERCa2 mRNA levels in fast extensor digitorum longus muscle (EDL), slow soleus muscle, and cardiac muscle in rats of different thyroid status. Hypothyroidism led in soleus to a marked decrease in SERCa1 mRNA and SERCa2 mRNA levels, in cardiac muscle SERCa2 mRNA decreased markedly, as previously shown by us, and in EDL SERCa1 mRNA decreased. These findings are compatible with a hypothyroidism induced decrease in SR Ca2+ ATPase activity and a delay in muscle relaxation. In contrast, SERCa2 mRNA of EDL, representing only a small percent of total SERCa mRNA in this muscle, increased to 175% of control values. Muscle specific and SERCa gene specific changes also occur after acute triiodothyronine (T3) administration to hypothyroid rats. T3 does not induce a significant change in SERCa1 or SERCa2 mRNA levels in soleus, but in the heart SERCa2 mRNA increases about 3-fold. In EDL, T3 increases SERCa1 mRNA from a hypothyroid level of 59 +/- 6% to 138 +/- 4% of control values but SERCa2 mRNA is decreased to 75 +/- 5% of control levels.(ABSTRACT TRUNCATED AT 250 WORDS)
甲状腺状态显著影响肌肉的收缩功能，而肌浆网（SR）Ca2+ATP酶活性的变化促成了这些改变。有两个独立的基因编码SR Ca2+ATP酶的主要亚型。在快肌中，肌浆内质网Ca2+ATP酶1型（SERCa1）是主要亚型，而在慢肌中SERCa2型（SERCa2）占主导。心肌只含有SERCa2。为了研究收缩功能变化的机制，我们对不同甲状腺状态大鼠的快趾长伸肌（EDL）、慢比目鱼肌和心肌中的SERCa1和SERCa2 mRNA水平进行了定量。甲状腺功能减退导致比目鱼肌中SERCa1 mRNA和SERCa2 mRNA水平显著降低，心肌中SERCa2 mRNA如我们之前所示显著降低，EDL中SERCa1 mRNA降低。这些发现与甲状腺功能减退导致SR Ca2+ATP酶活性降低和肌肉舒张延迟相一致。相比之下，EDL中的SERCa2 mRNA仅占该肌肉总SERCa mRNA的一小部分，增加到对照值的175%。对甲状腺功能减退大鼠急性给予三碘甲状腺原氨酸（T3）后，也会出现肌肉特异性和SERCa基因特异性变化。T3对比目鱼肌中SERCa1或SERCa2 mRNA水平无显著影响，但在心脏中SERCa2 mRNA增加约3倍。在EDL中，T3使SERCa1 mRNA从甲状腺功能减退水平的对照值的59±6%增加到138±4%，但SERCa2 mRNA降至对照水平的75±5%。（摘要截短于250字）
