Hobai I A, Bates J A, Howarth F C, Levi A J
Department of Physiology, School of Medical Sciences, University of Bristol, United Kingdom.
Am J Physiol. 1997 May;272(5 Pt 2):H2164-72. doi: 10.1152/ajpheart.1997.272.5.H2164.
We investigated the effect of external Cd2+ on the Na/Ca exchange and the L-type Ca channel current (ICa,L) in whole cell patch-clamped rabbit ventricular myocytes at 36 degrees C. After the interfering ion channels and the Na/K pump were blocked, the exchange current was measured as the membrane current that was inhibited by 5 mM nickel. External Cd2+ inhibited Na/Ca exchange with a dissociation constant (KD) of 320.6 +/- 12.4 microM and a Hill coefficient of 1.5 +/- 0.09 (n = 13 cells) and ICa,L with a KD of 2.14 +/- 0.15 microM and a Hill coefficient of 0.74 +/- 0.03 (n = 11 cells). We observed some overlap in the Cd2+ concentration that blocked each mechanism. Cd2+ (100-500 microM) is used commonly to block ICa,L completely. However, 100 microM Cd2+ also inhibits 20% of the Na/Ca exchange activity, whereas 500 microM Cd2+ inhibits 60%.
我们在36℃下，对全细胞膜片钳记录的兔心室肌细胞研究了细胞外Cd2+对钠钙交换和L型钙通道电流（ICa,L）的影响。在干扰离子通道和钠钾泵被阻断后，将交换电流测定为被5 mM镍抑制的膜电流。细胞外Cd2+抑制钠钙交换，解离常数（KD）为320.6±12.4 μM，希尔系数为1.5±0.09（n = 13个细胞），并抑制ICa,L，KD为2.14±0.15 μM，希尔系数为0.74±0.03（n = 11个细胞）。我们观察到阻断每种机制的Cd2+浓度存在一些重叠。Cd2+（100 - 500 μM）通常用于完全阻断ICa,L。然而，100 μM Cd2+也会抑制20%的钠钙交换活性，而500 μM Cd2+会抑制60%。
