Findlay I
Laboratoire de Physiologie Comparée (UA CNRS 1121), Université dé Paris XL, Orsay, France.
Pflugers Arch. 1988 Jul;412(1-2):37-41. doi: 10.1007/BF00583729.
K+ currents were recorded from ATP-sensitive channels in inside-out membrane patches excised from isolated rat ventricular myocytes. ATP-sensitive K+ channel inhibition could be evoked by ATP in the absence of magnesium where most ATP would be present as the free acid ATP4-. Channel inhibition was enhanced when the same total concentration of ATP was applied in the presence of magnesium, where most ATP would be bound as ATP.Mg. Dose-response relationships for ATP-sensitive K+ channel inhibition evoked by ATP had a Hill coefficient of 2 and Ki of 17 and 30 microM for ATP in the presence and absence of magnesium respectively. This was the obverse of the expected results if ATP4- were to be the sole form of ATP to effect channel closure. ATP-sensitive K+ channel inhibition evoked by ATP gamma S, AMP-PNP and AMP-PCP was also enhanced in the presence of magnesium. It is concluded that the ATP-sensitive K+ channel of rat ventricular myocytes binds and is closed by both the free-acid and divalent-cation-bound forms of ATP.
从分离的大鼠心室肌细胞切下的内向外膜片中记录ATP敏感性通道的钾离子电流。在不存在镁离子的情况下，ATP可诱发ATP敏感性钾通道抑制，此时大多数ATP以游离酸ATP4-形式存在。当在存在镁离子的情况下应用相同总浓度的ATP时，通道抑制增强，此时大多数ATP以ATP·Mg形式结合。ATP诱发的ATP敏感性钾通道抑制的剂量反应关系的希尔系数为2，在存在和不存在镁离子的情况下，ATP的抑制常数（Ki）分别为17和30微摩尔。如果ATP4-是影响通道关闭的唯一ATP形式，这与预期结果相反。在存在镁离子的情况下，ATPγS、AMP-PNP和AMP-PCP诱发的ATP敏感性钾通道抑制也增强。结论是大鼠心室肌细胞的ATP敏感性钾通道与ATP的游离酸形式和二价阳离子结合形式均结合并被其关闭。
