Carrier L, Villaz M, Dupont Y
Laboratoire de Biophysique Moléculaire et Cellulaire, LBIO/CENG, Grenoble, France.
Biochim Biophys Acta. 1991 May 7;1064(2):175-83. doi: 10.1016/0005-2736(91)90299-n.
Using the rapid filtration technique to investigate Ca2+ movements across the sarcoplasmic reticulum (SR) membrane, we compare the initial phases of Ca2+ release and Ca2+ uptake in malignant hyperthermia susceptible (MHS) and normal (N) pig SR vesicles. Ca2+ release is measured from passively loaded SR vesicles. MHS SR vesicles present a 2-fold increase in the initial rate of calcium release induced by 0.3 microM Ca2+ (20.1 +/- 2.1 vs. 6.3 +/- 2.6 nmol mg-1 s-1). Maximal Ca2+ release is obtained with 3 microM Ca2+. At this optimal concentration, rate of Ca2+ efflux in absence of ATP is 55 and 25 nmol mg-1 s-1 for MHS and N SR, respectively. Ca(2+)-induced Ca2+ release is inhibited by Mg2+ in a dose-dependent manner for both MHS and N pig SR vesicles (K1/2 = 0.2 mM). Caffeine (5 mM) and halothane (0.01% v/v) increase the Ca2+ sensitivity of Ca(2+)-induced Ca2+ release. ATP (5 mM) strongly enhances the rate of Ca2+ efflux (to about 20-40-fold in both MHS and N pig SR vesicles). Furthermore, both types of vesicles do not differ in their high-affinity site for ryanodine (Kd = 12 nM and Bmax = 6 pmol/mg), lipid content, ATPase activity and initial rate of Ca2+ uptake (0.948 +/- 0.034 vs. 0.835 +/- 0.130 mumol mg-1 min-1 for MHS and N SR, respectively). Our results show that MH syndrome is associated to a higher rate of Ca2+ release in the earliest phase of the calcium efflux.
我们运用快速过滤技术研究钙离子跨肌浆网（SR）膜的运动，比较了恶性高热易感（MHS）和正常（N）猪的SR囊泡中钙离子释放和摄取的初始阶段。钙离子释放是通过被动加载的SR囊泡来测量的。MHS SR囊泡在0.3微摩尔钙离子诱导下的初始钙离子释放速率增加了2倍（分别为20.1±2.1和6.3±2.6纳摩尔/毫克/秒）。最大钙离子释放量是在3微摩尔钙离子时获得的。在此最佳浓度下，无ATP时MHS和N SR的钙离子外流速率分别为55和25纳摩尔/毫克/秒。对于MHS和N猪SR囊泡，镁离子均以剂量依赖方式抑制钙离子诱导的钙离子释放（半数抑制浓度K1/2 = 0.2毫摩尔）。咖啡因（5毫摩尔）和氟烷（0.01%体积/体积）增加了钙离子诱导的钙离子释放的钙离子敏感性。ATP（5毫摩尔）强烈提高了钙离子外流速率（在MHS和N猪SR囊泡中均提高约20 - 40倍）。此外，两种类型的囊泡在对ryanodine的高亲和力位点（解离常数Kd = 12纳摩尔，最大结合量Bmax = 6皮摩尔/毫克）、脂质含量、ATP酶活性以及钙离子摄取的初始速率方面并无差异（MHS和N SR分别为0.948±0.034和0.835±0.130微摩尔/毫克/分钟）。我们的结果表明，恶性高热综合征与钙离子外流最早阶段更高的钙离子释放速率相关。
