Nichols C G, Niggli E, Lederer W J
Department of Physiology, University of Maryland, Baltimore 21201.
Pflugers Arch. 1990 Jan;415(4):510-2. doi: 10.1007/BF00373635.
We have used 'caged-ATP' to investigate the kinetic behavior of KATP channels in ventricular cells from rat heart. In whole cells, loaded with 'caged-ATP', an increase of intracellular [ATP] following a UV light flash produced a decrease of KATP channel current that was too slow (tau approximately 300 ms) to be explained by the expected time-course of ATP release (tau approximately 3 ms) and the time-course of channel blockade by ATP (tau approximately 20 ms). In isolated membrane patches, caged-ATP itself caused partial blockade of KATP) channels. Under these conditions, photorelease of ATP caused channel activity to decline further. The results suggest that caged-ATP can bind to the KATP) channel but, on binding, decreases the open probability to a lesser extent than does ATP. Additionally, the observations indicate that for photolytically-generated ATP to bind to the channel, caged-ATP must first unbind (slowly) from the channel. We conclude that 'caged-ATP' is not fully caged with respect to its allosteric action on the KATP channel.
我们已使用“笼锁ATP”来研究大鼠心脏心室细胞中KATP通道的动力学行为。在装载有“笼锁ATP”的全细胞中，紫外线闪光后细胞内[ATP]的增加导致KATP通道电流减小，但其速度过慢（时间常数约为300毫秒），无法用预期的ATP释放时间进程（时间常数约为3毫秒）和ATP对通道的阻断时间进程（时间常数约为20毫秒）来解释。在分离的膜片上，笼锁ATP本身会导致KATP通道部分阻断。在这些条件下，ATP的光释放会使通道活性进一步下降。结果表明，笼锁ATP可与KATP通道结合，但结合后降低开放概率的程度小于ATP。此外，观察结果表明，为使光解产生的ATP与通道结合，笼锁ATP必须首先（缓慢地）从通道上解离。我们得出结论，“笼锁ATP”对KATP通道的变构作用并未完全被“笼锁”。
