beta-Adrenergic stimulation induces acetylcholine to activate ATP-sensitive K+ current in cat atrial myocytes.
beta-Adrenergic stimulation induces acetylcholine to activate ATP-sensitive K+ current in cat atrial myocytes.
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DOI：
10.1161/01.res.77.3.565
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发表时间：
1995-09
影响因子：
20.1
通讯作者：
Y. G. Wang;S. Lipsius
中科院分区：
文献类型：
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作者：
Y. G. Wang;S. Lipsius
我们之前对心房肌细胞的研究表明，乙酰胆碱（ACh）增加K+电导的作用可以通过肌浆网（SR）预先加载Ca2+来增强。因此，本研究试图确定先前暴露于异丙肾上腺素（ISO）是否会增强乙酰胆碱诱导的K+电导增加及其潜在机制。用制氨抑素穿孔贴片全细胞构型记录猫心房肌细胞。电压钳形坡道（40 mV/s）用于评估膜的总电导。实验方案包括两次连续30秒的乙酰胆碱暴露（ACh1和ACh2），在无乙酰胆碱溶液中间隔6分钟的恢复期。一般来说，在ACh1和ACh2之间的一段时间内施加实验干预，如暴露于ISO，以确定它们对ACh1对ACh2反应的影响。在对照条件下，在恢复期间，无论是否激活L型Ca2+电流（ICa，L）， ACh1和ACh2诱导的K+电导都没有差异。当在恢复期施加1 μ mol/L ISO + ICa，L激活时，ACh2诱导的K+电导增加明显大于ACh1。由ISO增强的ach2诱导的K+电流具有时间独立性，可被10 μ mol/L格列本脲选择性阻断，因此被鉴定为ATP敏感的K+电流（IK，ATP）。ISO的影响诱导ACh2-activated本土知识,ATP是模仿1 mumol L / L forskolin或200 mumol / 8 - (4-chlorophenylthio)流派,但不是由0.5 mumol / L湾8644 K,并选择性地废除了(1)5 mumol / L thapsigargin或1 mumol / L阿诺定,代理防止SR Ca2 +的积累,(2)抑制L型钙离子电流(ICa L) 1 mumol / L nisoldipine或外部Ca2 + 0, (3) 50 mumol / L Rp-cAMPs cAMP-dependent蛋白激酶的抑制剂,或(4)2 mumol / L普萘洛尔。阿托品（1 μ mol/L）可消除所有乙酰胆碱诱导电流。此外，ach2激活的IK，ATP被0.2 mumol/L的M1毒蕈碱受体拮抗剂匹伦西平或0.1 mumol/L的calphostin C选择性阻断，后者是蛋白激酶C的选择性抑制剂。AFDX116 (100 mumol/L)， M2毒蕈碱受体拮抗剂，阻断了传统的ach激活的K+电流，显示出ach2激活的IK，ATP。这些结果表明，先前暴露于ISO会通过ach激活的IK，ATP增强ach诱导的K+电流的增加。（摘要删节为400字）
Our previous work on atrial myocytes suggested that the effect of acetylcholine (ACh) to increase K+ conductance can be potentiated by prior loading of the sarcoplasmic reticulum (SR) with Ca2+. The present study, therefore, sought to determine whether prior exposure to isoproterenol (ISO) potentiates ACh-induced increases in K+ conductance and the underlying mechanisms. A nystatin-perforated patch whole-cell configuration was used to record from cat atrial myocytes. Voltage-clamp ramps (40 mV/s) were used to assess total membrane conductance. The experimental protocol consisted of two consecutive 30-second ACh exposures (ACh1 and ACh2) separated by a 6-minute recovery period in ACh-free solution. In general, experimental interventions, such as exposure to ISO, were imposed during the period between ACh1 and ACh2 to determine their effects on the response to ACh2 in relation to ACh1. Under control conditions, K+ conductances induced by ACh1 and ACh2 were not different from one another with or without activation of L-type Ca2+ current (ICa,L) during the recovery period. When 1 mumol/L ISO plus ICa,L activation was imposed during the recovery period, ACh2 induced a significantly larger increase in K+ conductance than ACh1. The ACh2-induced K+ current potentiated by ISO was time independent and selectively blocked by 10 mumol/L glibenclamide and therefore identified as ATP-sensitive K+ current (IK,ATP). The effect of ISO to induce ACh2-activated IK,ATP was mimicked by 1 mumol/L forskolin or 200 mumol/L 8-(4-chlorophenylthio)-cAMP, but not by 0.5 mumol/L BAY K 8644, and was selectively abolished by (1) 5 mumol/L thapsigargin or 1 mumol/L ryanodine, agents that prevent accumulation of SR Ca2+, (2) inhibition of L-type Ca2+ current (ICa,L) by 1 mumol/L nisoldipine or zero external Ca2+, (3) 50 mumol/L Rp-cAMPs, an inhibitor of cAMP-dependent protein kinase A, or (4) 2 mumol/L propranolol. Atropine (1 mumol/L) abolished all ACh-induced currents. Moreover, ACh2-activated IK,ATP was selectively blocked by 0.2 mumol/L pirenzepine, an M1 muscarinic receptor antagonist, or 0.1 mumol/L calphostin C, a selective inhibitor of protein kinase C. AFDX116 (100 mumol/L), an M2 muscarinic receptor antagonist, blocked the conventional ACh-activated K+ current and revealed ACh2-activated IK,ATP. These results indicate that prior exposure to ISO potentiates ACh-induced increases in K+ current via ACh-activated IK,ATP.(ABSTRACT TRUNCATED AT 400 WORDS)