Mickelson J R, Ross J A, Hyslop R J, Gallant E M, Louis C F
Biochim Biophys Acta. 1987 Mar 12;897(3):364-76. doi: 10.1016/0005-2736(87)90434-2.
Sarcolemmal properties implicated in the skeletal muscle disorder, malignant hyperthermia (MH), were examined using sarcolemma-membrane vesicles isolated from normal and MH-susceptible (MHS) porcine skeletal muscle. MHS and normal sarcolemma did not differ in the distribution of the major proteins, cholesterol or phospholipid content, vesicle size and sidedness, (Na+ + K+)-ATPase activity, ouabain binding, or adenylate cyclase activity (total and isoproterenol sensitivity). The regulation of the initial rates of MHS and normal sarcolemmal ATP-dependent calcium transport (calcium uptake after 1 min) by Ca2+ (K1/2 = 0.64-0.81 microM), calmodulin, and cAMP-dependent protein kinase were similar. However, when sarcolemmal calcium content was measured at either 2 or 20 min after the initiation of active calcium transport, a significant difference between MHS and normal sarcolemmal calcium uptake became apparent, with MHS sarcolemma accumulating approximately 25% less calcium than normal sarcolemma. Calcium transport by MHS and normal sarcolemma, at 2 or 20 min, had a similar calmodulin dependence (C1/2 = 150 nM), and was stimulated to a similar extent by cAMP-dependent protein kinase or calmodulin. Halothane inhibited MHS and normal sarcolemmal active calcium uptake in a similar fashion (half-maximal inhibition at 10 mM halothane), while dantrolene (30 microM) and nitrendipine (1 microM) had little effect on either MHS or normal sarcolemmal calcium transport. After 20 min of ATP-supported calcium uptake, 2 mM EGTA plus 10 microM sodium orthovanadate were added to initiate sarcolemmal calcium efflux. Following an initial rapid phase of calcium release, an extended slow phase of calcium efflux (k = 0.012 min-1) was similar for both MHS and normal sarcolemma vesicles. We conclude that although a number of sarcolemmal properties, including passive calcium permeability, are normal in MH, a small but significant defect in MHS sarcolemmal ATP-dependent calcium transport may contribute to the abnormal calcium homeostasis and altered contractile properties of MHS skeletal muscle.
利用从正常和恶性高热易感性（MHS）猪骨骼肌分离的肌膜囊泡，研究了与骨骼肌疾病恶性高热（MH）相关的肌膜特性。MHS和正常肌膜在主要蛋白质的分布、胆固醇或磷脂含量、囊泡大小和方向性、（Na⁺ + K⁺）-ATP酶活性、哇巴因结合或腺苷酸环化酶活性（总量和异丙肾上腺素敏感性）方面没有差异。Ca²⁺（K1/2 = 0.64 - 0.81微摩尔）、钙调蛋白和cAMP依赖性蛋白激酶对MHS和正常肌膜ATP依赖性钙转运初始速率（1分钟后钙摄取）的调节相似。然而，当在主动钙转运开始后2分钟或20分钟测量肌膜钙含量时，MHS和正常肌膜钙摄取之间的显著差异变得明显，MHS肌膜积累的钙比正常肌膜少约25%。在2分钟或20分钟时，MHS和正常肌膜的钙转运对钙调蛋白的依赖性相似（C1/2 = 150纳摩尔），并且受到cAMP依赖性蛋白激酶或钙调蛋白的刺激程度相似。氟烷以类似方式抑制MHS和正常肌膜的主动钙摄取（在10毫摩尔氟烷时半数最大抑制），而丹曲林（30微摩尔）和尼群地平（1微摩尔）对MHS或正常肌膜的钙转运几乎没有影响。在ATP支持的钙摄取20分钟后，加入2毫摩尔乙二醇双乙胺醚四乙酸（EGTA）加10微摩尔原钒酸钠以启动肌膜钙外流。在最初快速的钙释放阶段之后，MHS和正常肌膜囊泡的钙外流延长的缓慢阶段（k = 0.012分钟⁻¹）相似。我们得出结论，尽管包括被动钙通透性在内的许多肌膜特性在MH中是正常的，但MHS肌膜ATP依赖性钙转运中一个小但显著的缺陷可能导致MHS骨骼肌异常的钙稳态和改变的收缩特性。
