Ervasti J M, Mickelson J R, Louis C F
Department of Biochemistry, University of Minnesota, St. Paul 55108.
Arch Biochem Biophys. 1989 Mar;269(2):497-506. doi: 10.1016/0003-9861(89)90133-1.
Transverse tubule (TT) calcium transport and permeability were examined in the inherited skeletal muscle disorder malignant hyperthermia (MH). ATP-dependent calcium uptake by TT vesicles isolated from normal and MH-susceptible (MHS) pig muscle had a similar dependence on ionized Ca2+ concentration (K1/2 for Ca2+ of 0.21 +/- 0.04 and 0.25 +/- 0.05 microM for MHS and normal TT, respectively), as well as a similar Vmax (20.9 +/- 2.0 and 23.7 +/- 4.5 nmol Ca/mg protein/min for MHS and normal TT, respectively). Furthermore, the stimulation of calcium uptake by either calmodulin or cAMP-dependent protein kinase was similar in normal and MHS TT. Halothane concentrations greater than 2 mM inhibited calcium uptake by either normal or MHS TT to a similar extent (IC50 = 8 mM). Dantrolene (10 microM), nitrendipine (1 microM), and Bay K 8644 (1 microM) had no significant effect on either the initial rates of calcium uptake or maximal calcium accumulation of either MHS or normal TT vesicles. However, in the absence of any added agents, maximum calcium accumulation by MHS TT was significantly less than by normal TT (90 +/- 10 versus 130 +/- 9 nmol Ca/mg protein after 15 min of uptake). This difference was not due to an increased permeability of MHS TT to calcium, nor was it due to a difference in the sarcoplasmic reticulum contamination (less than 5%) of the MHS and normal preparations. Although our results indicate there is no significant defect in MHS TT calcium regulation, the diminished maximum calcium accumulation by MHS TT may contribute to the abnormal sarcoplasmic calcium homeostasis in skeletal muscle during an MH crisis.
在遗传性骨骼肌疾病恶性高热（MH）中，对横管（TT）的钙转运和通透性进行了研究。从正常猪肌肉和恶性高热易感（MHS）猪肌肉中分离出的TT囊泡，其ATP依赖性钙摄取对游离Ca2+浓度的依赖性相似（MHS和正常TT的Ca2+的K1/2分别为0.21±0.04和0.25±0.05微摩尔），Vmax也相似（MHS和正常TT分别为20.9±2.0和23.7±4.5纳摩尔钙/毫克蛋白/分钟）。此外，正常和MHS TT中，钙调蛋白或cAMP依赖性蛋白激酶对钙摄取的刺激作用相似。大于2毫摩尔的氟烷浓度对正常或MHS TT的钙摄取抑制程度相似（IC50 = 8毫摩尔）。丹曲林（10微摩尔）、尼群地平（1微摩尔）和Bay K 8644（1微摩尔）对MHS或正常TT囊泡的钙摄取初始速率或最大钙积累均无显著影响。然而，在没有添加任何试剂的情况下，MHS TT的最大钙积累明显低于正常TT（摄取15分钟后，分别为90±10和130±9纳摩尔钙/毫克蛋白）。这种差异不是由于MHS TT对钙的通透性增加，也不是由于MHS和正常制剂的肌浆网污染存在差异（小于5%）。尽管我们的结果表明MHS TT的钙调节没有明显缺陷，但MHS TT最大钙积累的减少可能导致MH危象期间骨骼肌中异常的肌浆钙稳态。
