Park K S, Kim T K, Kim D H
Department of Life Science, Kwangju Institute of Science and Technology, Kwangju 500-712, Korea.
Am J Physiol. 1999 Mar;276(3):H865-72. doi: 10.1152/ajpheart.1999.276.3.H865.
Chronic treatment with cyclosporin A (CsA) has been reported (H. S. Banijamali, M. H. ter Keurs, L. C. Paul, and H. E. ter Keurs. Cardiovasc. Res. 27: 1845-1854, 1993; I. Kingma, E. Harmsen, H. E. ter Keurs, H. Benediktsson, and L. C. Paul. Int. J. Cardiol. 31: 15-22, 1991) to induce reversible alterations of contractile properties in rat hearts. To define the molecular mechanisms underlying the physiological alterations, the Ca2+-release channel (CRC) and Ca2+-ATPase from sarcoplasmic reticulum in rats were examined. Ryanodine binding to whole homogenates of rat hearts shows time- and dose-dependent alterations in CRC properties by CsA. On 3 wk of treatment with 15 mg CsA. kg body wt-1. day-1, 1) maximal ryanodine binding (Bmax) decreased, 2) the dissociation constant of ryanodine (Kd) increased, 3) caffeine sensitivity of CRC increased, and 4) ruthenium red sensitivity of CRC decreased. On the other hand, Bmax and Kd of ryanodine binding in rat skeletal muscles were not changed. Ryanodine-sensitive oxalate-supported Ca2+ uptake in whole homogenates was lower in CsA-treated rat hearts than in control hearts, whereas total Ca2+ uptake in the presence of 500 M ryanodine was not changed. Functional experiments with rapamycin and Western blot analysis suggest that the CsA-induced alteration of ryanodine binding is due at least in part to an upregulation of calcineurin. The heart muscle-specific alterations of CRC could be responsible for the previously reported contractile changes of CsA-treated rat hearts.
据报道，长期使用环孢素A（CsA）治疗（H. S. Banijamali、M. H. ter Keurs、L. C. Paul和H. E. ter Keurs，《心血管研究》27: 1845 - 1854，1993；I. Kingma、E. Harmsen、H. E. ter Keurs、H. Benediktsson和L. C. Paul，《国际心脏病学杂志》31: 15 - 22，1991）可导致大鼠心脏收缩特性的可逆性改变。为了确定这些生理改变背后的分子机制，对大鼠肌浆网中的钙释放通道（CRC）和钙ATP酶进行了检测。雷帕霉素与大鼠心脏全匀浆的结合显示，CsA可使CRC特性发生时间和剂量依赖性改变。在用15 mg CsA·kg体重⁻¹·天⁻¹治疗3周后，1）雷帕霉素最大结合量（Bmax）降低，2）雷帕霉素解离常数（Kd）增加，3）CRC对咖啡因的敏感性增加，4）CRC对钌红的敏感性降低。另一方面，大鼠骨骼肌中雷帕霉素结合的Bmax和Kd未发生变化。在CsA处理的大鼠心脏全匀浆中，雷帕霉素敏感的草酸盐支持的钙摄取低于对照心脏，而在存在500 μM雷帕霉素时总钙摄取未改变。用雷帕霉素进行的功能实验和蛋白质免疫印迹分析表明，CsA诱导的雷帕霉素结合改变至少部分归因于钙调神经磷酸酶的上调。CRC的心肌特异性改变可能是先前报道的CsA处理大鼠心脏收缩变化的原因。
