Wagner-Mann C, Bowman L, Sturek M
Department of Physiology, School of Medicine, University of Missouri, Columbia 65211.
Am J Physiol. 1991 Apr;260(4 Pt 1):C763-70. doi: 10.1152/ajpcell.1991.260.4.C763.
Intracellular free Ca concentrations (Cai) were determined by fura-2 microfluorometry in single freshly dispersed cells to differentiate endothelin (ET)-induced Ca release from Ca influx through voltage-gated Ca channels (VGCC). In physiological solution ET (10(-8) M) significantly (P less than 0.05) increased Cai 23 +/- 3% (+/- SE) above baseline; this increase was not significantly attenuated by 2 x 10(-4) M lanthanum, a blocker of VGCC, or Ca-free solution. When the sarcoplasmic reticulum was depleted of Ca by prolonged treatment with 5 x 10(-3) M caffeine, depolarization with 80 mM K (80K; or 30K) plus ET did not increase Cai above that induced by 80K (or 30K) in caffeine alone. In contrast, 10(-6) M BAY K 8644, instead of ET in the protocol, significantly (P less than 0.05) increased Cai above that induced by 80K (or 30K). ET released Ca from the caffeine-sensitive internal store but was not rapid and transient like caffeine-induced release, which elicited a peak Cai increase in less than 1 min; instead, release was more gradual and prolonged with Cai peaking in greater than 2 min, thus resembling the response to 10(-5) M ryanodine. With two ET exposures, either a transient nonrepeatable increase in Cai or a delayed, but sustained, increase in Cai resulted, similar to the response to ryanodine. These data indicate that in freshly dispersed bovine cells the predominant mechanism by which ET increases Cai is release of Ca from the sarcoplasmic reticulum; if any increase in L-type voltage-gated Ca influx occurred, it was minimal and matched by efflux.
通过fura - 2显微荧光测定法在单个新鲜分散的细胞中测定细胞内游离钙浓度（Cai），以区分内皮素（ET）诱导的钙释放与通过电压门控钙通道（VGCC）的钙内流。在生理溶液中，ET（10⁻⁸ M）使Cai显著（P < 0.05）比基线水平升高23 ± 3%（± SE）；这种升高并未被2×10⁻⁴ M镧（一种VGCC阻滞剂）或无钙溶液显著减弱。当用5×10⁻³ M咖啡因长时间处理使肌浆网中的钙耗尽后，用80 mM K（80K；或30K）加ET进行去极化处理，Cai升高幅度并不高于仅用咖啡因处理的80K（或30K）所诱导的水平。相反，在实验方案中用10⁻⁶ M BAY K 8644替代ET，Cai升高幅度显著（P < 0.05）高于80K（或30K）所诱导的水平。ET从对咖啡因敏感的内部储存库中释放钙，但不像咖啡因诱导的释放那样快速且短暂，咖啡因诱导的释放会在不到1分钟内使Cai升高达到峰值；相反，ET诱导的释放更为缓慢且持续时间更长，Cai在2分钟以上达到峰值，因此类似于对10⁻⁵ M兰尼碱的反应。进行两次ET刺激时，要么Cai出现短暂的不可重复升高，要么出现延迟但持续的升高，类似于对兰尼碱的反应。这些数据表明，在新鲜分散的牛细胞中，ET升高Cai的主要机制是从肌浆网中释放钙；如果L型电压门控钙内流有任何增加，其幅度也极小且与外流相匹配。
