NUCLEOTIDE MODULATION OF THE ACTIVITY OF RAT-HEART ATP-SENSITIVE K+ CHANNELS IN ISOLATED MEMBRANE PATCHES
NUCLEOTIDE MODULATION OF THE ACTIVITY OF RAT-HEART ATP-SENSITIVE K+ CHANNELS IN ISOLATED MEMBRANE PATCHES
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DOI：
10.1113/jphysiol.1989.sp017869
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发表时间：
1989-12-01
影响因子：
5.5
通讯作者：
NICHOLS, CG
中科院分区：
文献类型：
--
作者：
LEDERER, WJ;NICHOLS, CG
在分离的大鼠心室肌细胞膜片上，我们测量了KATP通道活性对ATP的依赖性，以及不同代谢物对这种关系的影响。ATP对KATP通道活性的抑制可描述为[ATP]的S型函数，希尔系数(HATP)为2，在总[Mg~(2+)]为0 mM或0.5 mM时，当(KI，ATP)为25µm时，抑制作用为半最大值。非水解性ATP类似物AMP-PNP对KI，AMP-PNP=60微米和HAMP-PNP=2也有抑制作用。酸中毒使KI，ATP从pH 7.25的25微米增加到pH 6.25的50微米，但对20 mM的磷酸盐和乳酸无影响。在没有ATP或Mg~(2+)的情况下，ADP3~-抑制通道活动的KI，ADP=275µm，HADP=1.2。其他嘌呤和嘧啶三磷酸盐、二磷酸和一磷酸也抑制该通道，其抑制效果明显顺序为：ATP>；AMP-PMP>；ADP>；CTP>；GDP=AMP=ITP。在无镁离子存在时，GTP、ITP、CTP、GDP、ADP或AMP对通道的抑制与ATP的抑制相加。在0.5 mM-Mg~(2+)和40µM-ATP存在下，GTP、GMP和AMP的抑制作用与ATP的抑制作用是相加的。然而，在存在ATP的情况下，二磷酸ADP和GDP反常地增加了通道的活性。这种通道活性的增加似乎是KI、ATP竞争性增加的结果。镁ADP似乎不会对通道活动造成任何抑制。我们的结论是，在心肌组织中，KATP通道受[ATP]的调节，这种调节对其他细胞内核苷酸、镁离子和pH敏感，但对磷酸盐或乳酸不敏感。一个简单的相互作用的双结合位点模型与我们观察到的核苷酸依赖的调控是一致的。
We have measured the ATP dependence of KATP channel activity, and the effect of various metabolites on this relationship, in inside-out membrane patches isolated from rat ventricular myocytes. The inhibition of KATP channel activity by ATP could be described as a sigmoid function of [ATP] with a Hill coefficient (HATP) of 2 and a half-maximal inhibition at an ATP concentration of (Ki, ATP) of 25 .mu.M, in the presence of 0 mM, or 0.5 mM, total [Mg2+]. The non-hydrolysable ATP analogue, AMP-PNP, also inhibited the channel with Ki, AMP-PNP = 60 .mu.M and HAMP-PNP = 2. Acidosis caused a small, but significant, incrase in Ki, ATP from 25 .mu.M at pH 7.25 to 50 .mu.M at pH 6.25, but phosphate and lactate were without effect (at 20 mM) on channel activity. In the absence of ATP or Mg2+, ADP3- inhibited channel activity with Ki, ADP = 275 .mu.M, and HADP = 1.2. Other purine and pyrimidine triphosphates, diphosphates and monophosphates also inhibited the channel with apparent order of inhibitory effectiveness ATP > AMP-PMP > ADP > CTP > GDP = AMP = ITP. In the absence of Mg2+, but in the presence of 40 .mu.M-ATP, channel inhibition by GTP, ITP, CTP, GDP, ADP or AMP was additive with inhibition by ATP. In the presence of 0.5 mM-Mg2+ and 40 .mu.M-ATP, inhibition by GTP, GMP and AMP was still additive with inhibition by ATP. The diphosphates ADP and GDP, however, paradoxically increased channel activity in the presence of ATP. This increase in channela activity appeared to result from a competitive increase in Ki, ATP. MgADP did not appear to cause any inhibition of channel activity. We conclude that, in cardiac tissue, KATP channels are regulated by [ATP], and that this regulation is sensitive to other intracellular nucleotides, Mg2+, and pH, but not to phosphate or lactate. A simple, interactive two binding-site model is consistent with the nucleotide-dependent regulation that we observe.