Modulation of voltage‐dependent Ba2+ currents in the guinea‐pig gastric antrum by cyclic nucleotide‐dependent pathways
Modulation of voltage‐dependent Ba2+ currents in the guinea‐pig gastric antrum by cyclic nucleotide‐dependent pathways
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DOI：
10.1038/sj.bjp.0706295
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发表时间：
2005-09
影响因子：
7.3
通讯作者：
Hai‐Lei Zhu;G. Hirst;Y. Ito;N. Teramoto
中科院分区：
文献类型：
--
作者：
Hai‐Lei Zhu;G. Hirst;Y. Ito;N. Teramoto
我们研究了cAMP和cGMP依赖性通路的激活是否改变了使用膜片钳技术从豚鼠胃肌细胞记录的电压依赖性Ba 2+电流（IBa）的特性。所有实验均在分散于豚鼠胃窦环形层的单个平滑肌细胞上进行。二丁酰cAMP（db-cAMP，0.1-1 mM）（一种cAMP的膜渗透酯）和异丙肾上腺素（一种选择性β兴奋剂）均以浓度依赖性方式抑制IB。毛喉素，但不包括双脱氧毛喉素（毛喉素的一种无活性异构体），抑制IBa的峰值振幅。在Rp-cAMP或PKA存在下，（cAMP依赖性蛋白激酶）抑制肽5 - 24（PKA-IP），毛喉素和db-cAMP都不能抑制IBa。当PKA的催化亚基被包含在移液管中时，IB的峰幅度逐渐降低。硝普钠（0.1-1 mM）和8-Br-cGMP（0.1 -1 mM）也以浓度依赖性方式抑制IBa，而forskolin或db-cAMP对IBa的抑制作用不受cGMP依赖性蛋白激酶（PKG）抑制剂的影响。 同样，8-Br-cGMP对IBa的抑制作用也没有被PKA-IP改变。膜可透性环核苷酸db-cAMP和8-Br-cGMP几乎没有引起稳态失活和再激活曲线的电压依赖性变化。膜可透性环核苷酸db-cAMP或8-Br-cGMP对IBa都没有相加的抑制作用。这些结果表明豚鼠胃窦中存在两种不同的环核苷酸依赖性途径，并且这两者都以独立的方式抑制IB.British Journal of Pharmacology（2005）146，129-138。doi：10.1038/sj.bjp.0706295
We have investigated whether the activation of cAMP‐ and cGMP‐dependent pathways modifies the properties of voltage‐dependent Ba2+currents (IBa) recorded from guinea‐pig gastric myocytes using patch‐clamp techniques. All experiments were carried on single smooth muscle cells, dispersed from the circular layer of the guinea‐pig gastric antrum.Both dibutyryl cAMP (db‐cAMP, 0.1–1 mM), a membrane‐permeable ester of cAMP, and isoproterenol, a selectiveβ‐stimulant, inhibitedIBain a concentration‐dependent manner.Forskolin, but not dideoxy‐forskolin, an inactive isomer of forskolin, inhibited the peak amplitude ofIBa.In the presence of either Rp‐cAMP or the PKA (cAMP‐dependent protein kinase) inhibitor peptide 5‐24 (PKA‐IP), neither forskolin nor db‐cAMP inhibitedIBa.After establishing a conventional whole‐cell recording, the peak amplitude ofIBagradually decreased when the catalytic subunit of PKA was included in the pipette. The further application of Rp‐cAMP reversibly enhancedIBa.Sodium nitroprusside (0.1–1 mM) and 8‐Br‐cGMP (0.1–1 mM) also inhibitedIBain a concentration‐dependent manner.The inhibitory effects of forskolin or db‐cAMP onIBawere not significantly changed by pretreatment with a cGMP‐dependent protein kinase (PKG) inhibitor. Similarly, the inhibitory actions of 8‐Br‐cGMP onIBawere not modified by PKA‐IP.The membrane‐permeable cyclic nucleotides db‐cAMP and 8‐Br‐cGMP caused little shift of the voltage dependence of the steady‐state inactivation and reactivation curves.Neither of the membrane‐permeable cyclic nucleotides db‐cAMP or 8‐Br‐cGMP had additive inhibitory effects onIBa.These results indicate that two distinct cyclic nucleotide‐dependent pathways are present in the guinea‐pig gastric antrum, and that both inhibitedIBain an independent manner.British Journal of Pharmacology(2005)146, 129–138. doi:10.1038/sj.bjp.0706295