Klieber H G, Daut J
Physiologisches Institut, Technischen Universität München, Germany.
Cardiovasc Res. 1994 Jun;28(6):823-30. doi: 10.1093/cvr/28.6.823.
The aim was to isolate terminal arterioles from guinea pig heart, to describe their basic electrical properties, and to obtain evidence for the presence of KATP channels in microvascular coronary smooth muscle cells.
Terminal arterioles of 20-50 microns diameter were obtained by enzymatic digestion of isolated perfused hearts. The isolated arterioles were viable for up to 8 h and constricted upon application of high potassium solution. Whole cell clamp experiments on smooth muscle cells of these arterioles were performed at room temperature.
The resting potential of coronary smooth muscle cells in terminal arterioles showed a bimodal distribution with one peak at -23(SD 8) mV and the other peak at -61(4) mV. Application of glibenclamide (50 microM) to the latter group of arterioles produced a depolarisation to -37(8) mV; application of cromakalim (1 microM) produced a hyperpolarisation to -71(1) mV. The current changes associated with voltage steps and slow voltage ramps in the range -120 to +40 mV indicated that the smooth muscle cells in the arterioles were coupled electrically. The steady state current-voltage relation was sigmoid with a flat region in the range -50 to -30 mV. In the presence of 2-50 microM glibenclamide the slope resistance at potentials negative to -50 mV and positive to -30 mV was markedly increased. In the presence of 1 microM cromakalim the slope resistance was decreased and the current-voltage relation at negative potentials became nearly linear. The crossover point of the current-voltage relations measured under control conditions and in the presence of glibenclamide was near the calculated potassium equilibrium potential.
Glibenclamide closes and cromakalim opens potassium channels in smooth muscle cells of coronary arterioles. The voltage dependence of the steady state current changes suggests that the current activated by cromakalim is not carried by the same channels as the current inhibited by glibenclamide. The glibenclamide sensitive channels make a significant contribution to the membrane potential of isolated arterioles.
从豚鼠心脏分离终末小动脉，描述其基本电特性，并获取微血管冠状动脉平滑肌细胞中存在ATP敏感性钾通道（KATP通道）的证据。
通过酶消化分离的灌注心脏获得直径为20 - 50微米的终末小动脉。分离出的小动脉可存活长达8小时，并在应用高钾溶液时收缩。在室温下对这些小动脉的平滑肌细胞进行全细胞钳实验。
终末小动脉中冠状动脉平滑肌细胞的静息电位呈双峰分布，一个峰值在 - 23（标准差8）毫伏，另一个峰值在 - 61（4）毫伏。对后一组小动脉应用格列本脲（50微摩尔）导致去极化至 - 37（8）毫伏；应用克罗卡林（1微摩尔）导致超极化至 - 71（1）毫伏。与 - 120至 + 40毫伏范围内的电压阶跃和缓慢电压斜坡相关的电流变化表明小动脉中的平滑肌细胞存在电耦合。稳态电流 - 电压关系呈S形，在 - 50至 - 30毫伏范围内有一个平坦区域。在存在2 - 50微摩尔格列本脲的情况下，在电位低于 - 50毫伏和高于 - 30毫伏时的斜率电阻明显增加。在存在1微摩尔克罗卡林的情况下，斜率电阻降低，负电位下的电流 - 电压关系几乎变为线性。在对照条件下和存在格列本脲时测量的电流 - 电压关系的交叉点接近计算出的钾平衡电位。
格列本脲关闭冠状动脉小动脉平滑肌细胞中的钾通道，而克罗卡林打开这些通道。稳态电流变化的电压依赖性表明，克罗卡林激活的电流与格列本脲抑制的电流不是由相同的通道传导。格列本脲敏感通道对分离小动脉的膜电位有重要贡献。
