beta-adrenergic and cholinergic modulation of the inwardly rectifying K+ current in guinea-pig ventricular myocytes.
beta-adrenergic and cholinergic modulation of the inwardly rectifying K+ current in guinea-pig ventricular myocytes.
复制标题
豚鼠心室肌细胞内向整流 K 电流的 β-肾上腺素能和胆碱能调节。
DOI：
10.1113/jphysiol.1995.sp020841
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
TenEick,RE
中科院分区：
文献类型：
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作者：
Koumi,S;Wasserstrom,JA;TenEick,RE
1.采用全细胞膜片钳技术研究了β-肾上腺素能和胆碱能对豚鼠心室肌细胞内向整流钾离子传导（gK1）的调节。2.在不含Cl（-）的溶液中或存在9-蒽羧酸或Co2+的情况下，浴用异丙肾上腺素（Iso）部分抑制稳态全细胞电导（gss），该电导由膜电压（Vm）负于钾平衡电位（EK）时的稳态电流（Iss）-电压（Iss-V）曲线计算得出。当细胞外[K +]为20 mM时，当Vm对EK为阳性时，Iss也受到抑制。Iso敏感的gss组分表现出内向整流K+电导（gK1）的特征。3. Iso诱导的gK1抑制是可逆的，具有浓度依赖性，可被普萘洛尔阻断，可被毛喉素和二丁酰cAMP模拟，并可通过在移液器溶液中加入cAMP依赖性蛋白激酶（PKA）抑制剂来预防。这些发现表明PKA介导了Iso诱导的gK1抑制。4. Iso诱导抑制的浓度依赖性的表观解离常数（KD）为0.035 μ M，希尔系数约为1.0。最大Iso浓度（1 μ M）抑制gK1 40 +/-4.1%（平均值+/-S.E.M.; n = 13）。5.浴用乙酰胆碱（ACh，0.1 μ M或更高）可拮抗Iso诱导的（1 μ M）gK1抑制;[ACh]> 1.0 μ M可拮抗88 +/-2.1%（n = 10）的抑制。ACh增加了Iso抑制Iso敏感性gK1的KD，也降低了Iso诱导的最大抑制作用。6. ACh诱导的拮抗作用可以通过用百日咳毒素（PTX）预孵育肌细胞来消除，这表明涉及毒蕈碱受体偶联的PTX敏感性G蛋白Gi。7. ACh（10 μ M）还拮抗了约70%的二丁酰环AMP（1 mM）诱导的gK1抑制（n = 3），表明ACh诱导的拮抗作用不仅仅是通过激活的Gi抑制Iso介导的腺苷酸环化酶激活。8.细胞内应用冈田酸（OkA，1 μ M）没有改变gK1（对照= 134 +/-5.1 nS vs. OkA = 136 +/-6.1 nS），但Iso诱导的gK1降低在存在OkA时（42.1 +/-2.4 nS，n = 5）比不存在OkA时（54.0 +/-2.2 nS，n = 10）更少（P <0.001）。然而，ACh（10 μ M）未能拮抗Iso诱导的抑制与OKA的存在，这表明蛋白磷酸酶的参与。
1. Whole‐cell patch‐clamp technique was used to study the beta‐adrenergic and cholinergic regulation of the inwardly rectifying K+ conductance (gK1) in isolated guinea‐pig ventricular myocytes. 2. In Cl(‐)‐free solutions or in the presence of 9‐anthracenecarboxylic acid or Co2+, bath‐applied isoprenaline (Iso) partially inhibited the steady‐state whole‐cell conductance (gss) calculated from the steady‐state current (Iss)‐voltage (Iss‐V) curve at membrane voltages (Vm) negative to the equilibrium potential for potassium (EK). Iss was also inhibited at Vm positive to EK when the extracellular [K+] was 20 mM. The Iso‐sensitive component of gss exhibited the characteristics of the inwardly rectifying K+ conductance (gK1). 3. The Iso‐induced inhibition of gK1 was reversible, concentration dependent, blocked by propranolol, mimicked by both forskolin and dibutyryl cAMP, and prevented by including a cAMP‐dependent protein kinase (PKA) inhibitor in the pipette solution. These findings suggest that PKA mediates the Iso‐induced inhibition of gK1. 4. The apparent dissociation constant (KD) for the concentration dependence of Iso‐induced inhibition was 0.035 microM and the Hill coefficient was approximately 1.0. A maximal Iso concentration (1 microM) inhibited gK1 by 40 +/‐ 4.1% (mean +/‐ S.E.M.; n = 13). 5. Bath application of acetylcholine (ACh, 0.1 microM or more) antagonized the Iso‐induced (1 microM) inhibition of gK1; [ACh] > 1.0 microM antagonized 88 +/‐ 2.1% (n = 10) of the inhibition. ACh increased the KD for Iso to inhibit Iso‐sensitive gK1 and also reduced the maximal Iso‐induced inhibition. 6. ACh‐induced antagonism could be abolished by pre‐incubating myocytes with pertussis toxin (PTX), suggesting that a muscarinic receptor‐coupled, PTX‐sensitive G protein, Gi, is involved. 7. ACh (10 microM) also antagonized approximately 70% of the dibutyryl cyclic AMP (1 mM)‐induced inhibition of gK1 (n = 3), suggesting that the ACh‐induced antagonism involves more than simply inhibiting the Iso‐mediated activation of adenylyl cyclase via the activated Gi. 8. Intracellularly applied okadaic acid (OkA, 1 microM) did not alter gK1 (control = 134 +/‐ 5.1 nS vs. OkA = 136 +/‐ 6.1 nS), but the Iso‐induced decrease in gK1 was less (P < 0.001) with OkA present (42.1 +/‐ 2.4 nS, n = 5) than when absent (54.0 +/‐ 2.2 nS, n = 10). However, ACh (10 microM) failed to antagonize Iso‐induced inhibition with OkA present, suggesting involvement of a protein phosphatase.