Sarcoplasmic reticulum Ca2+ pumping kinetics regulates timing of local Ca2+ releases and spontaneous beating rate of rabbit sinoatrial node pacemaker cells.
Sarcoplasmic reticulum Ca2+ pumping kinetics regulates timing of local Ca2+ releases and spontaneous beating rate of rabbit sinoatrial node pacemaker cells.
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DOI：
10.1161/circresaha.110.220517
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发表时间：
2010-09-17
影响因子：
20.1
通讯作者：
Lakatta EG
中科院分区：
文献类型：
--
作者：
Vinogradova TM;Brochet DX;Sirenko S;Li Y;Spurgeon H;Lakatta EG
窦房结细胞 (SANC) 在舒张末期去极化 (DD) 期间从肌浆网 (SR) 产生局部肌膜下 Ca2+ 释放 (LCR)。 LCR 激活内向 Na+-Ca2+ 交换电流 (INCX)，从而加速 DD 速率，从而引发下一个动作电位 (AP)。 LCR 周期，即 AP 诱导的 Ca2+ 瞬变和 LCR 出现之间的延迟，定义了 DD INCX 晚期激活的时间。然而，控制 LCR 周期的机制仍不清楚。确定 LCR 周期对 SR Ca2+ 再充盈动力学的依赖性，并建立 SR Ca2+ 补充调节、LCR 周期和自发周期长度之间的联系。分别使用穿孔贴片和共聚焦显微镜记录自发 AP 和 SR 管腔或胞质 Ca2+。 AP 诱导的 Ca2+ 瞬变后 SR Ca2+ 补充 90% 的时间与胞质 Ca2+ 瞬变 (T-90C) 衰减 90% 的时间高度相关。局部 SR Ca2+ 消耗反映了其胞质对应物 LCR，并在 SR Ca2+ 再填充后发生。环吡嗪酸 (CPA) 对 SR Ca2+ 泵的抑制作用剂量依赖性地抑制自发 SANC 放电高达约 50%。 CPA 和由 β-AR 刺激、磷酸二酯酶或 PKA 抑制产生的受磷蛋白磷酸化的分级变化改变了 T-90C，并按比例改变了 LCR 周期和自发周期长度 (R2=0.98)。 LCR 周期是自发 SANC 周期长度的关键决定因素，由 SR Ca2+ 补充速率定义，这主要取决于 SR 泵送速率、可用于泵送的 Ca2+（由 L 型 Ca2+ 通道提供）和 RyR Ca2+ 释放通量，其中每一个都受 cAMP 介导的 PKA 依赖性磷酸化调节。
Sinoatrial node cells (SANC) generate local, subsarcolemmal Ca2+ releases (LCRs) from sarcoplasmic reticulum (SR) during late diastolic depolarization (DD). LCRs activate an inward Na+-Ca2+ exchange current (INCX) which accelerates DD rate, prompting the next action potential (AP). The LCR period, i.e., a delay between AP-induced Ca2+ transient and LCR appearance, defines the time of late DD INCX activation. Mechanisms that control the LCR period, however, are still unidentified. To determine dependence of the LCR period on SR Ca2+ refilling kinetics and establish links between regulation of SR Ca2+ replenishment, LCR period and spontaneous cycle length. Spontaneous APs and SR luminal or cytosolic Ca2+ were recorded using perforated patch and confocal microscopy, respectively. Time to 90% replenishment of SR Ca2+ following AP-induced Ca2+ transient was highly correlated with the time to 90% decay of cytosolic Ca2+ transient (T-90C). Local SR Ca2+ depletions mirror their cytosolic counterparts, LCRs, and occur following SR Ca2+ refilling. Inhibition of SR Ca2+ pump by cyclopiazonic acid (CPA) dose-dependently suppressed spontaneous SANC firing up to ~50%. CPA and graded changes in phospholamban phosphorylation produced by β-AR stimulation, phosphodiesterase or PKA inhibition shifted T-90C and proportionally shifted the LCR period and spontaneous cycle length (R2=0.98). The LCR period, a critical determinant of the spontaneous SANC cycle length, is defined by the rate of SR Ca2+ replenishment, which is critically dependent on SR pumping rate, Ca2+ available for pumping, supplied by L-type Ca2+ channel, and RyR Ca2+ release flux each of which is modulated by cAMP-mediated PKA-dependent phosphorylation.