Takens-Kwak B R, Jongsma H J, Rook M B, Van Ginneken A C
Department of Physiology, University of Amsterdam, The Netherlands.
Am J Physiol. 1992 Jun;262(6 Pt 1):C1531-8. doi: 10.1152/ajpcell.1992.262.6.C1531.
The influence of heptanol on gap junctional and non-junctional membrane currents was studied in cultured neonatal rat heart cells using both the whole cell and perforated patch voltage-clamp method. With both methods, exposure to heptanol produced a dose-dependent decrease in the junctional current (dissociation constant = 0.54 and 1.20 mM for whole cell and perforated patch experiments, respectively). Heptanol-induced uncoupling was reversible. In the same concentration range, heptanol reduced all nonjunctional membrane ionic currents examined. This suggests that heptanol does not act specifically on gap junction channels but rather on the structure of the lipid membrane. This hypothesis is strengthened by the observation that in monolayer cultures of neonatal rat heart cells fluorescence steady-state anisotropy decreased proportional with increasing the heptanol concentration in the bath. Single-channel conductances (gamma j) were identical with both recording methods (21 and 40-45 pS); heptanol did not alter gamma j. Under conditions of reduced junctional coupling induced by heptanol, junctional conductance (gj) displayed voltage sensitivity at values of gj at which no voltage sensitivity could be observed under control conditions. These results suggest that heptanol-dependent uncoupling was caused by a decrease in open probability of the gap junction channels.
采用全细胞膜片钳和穿孔膜片钳电压钳技术，研究了庚醇对培养的新生大鼠心脏细胞缝隙连接电流和非连接膜电流的影响。使用这两种方法时，暴露于庚醇都会使连接电流呈剂量依赖性降低（全细胞实验和穿孔膜片钳实验的解离常数分别为0.54和1.20 mM）。庚醇诱导的解偶联是可逆的。在相同浓度范围内，庚醇降低了所有检测的非连接膜离子电流。这表明庚醇并非特异性作用于缝隙连接通道，而是作用于脂质膜的结构。新生大鼠心脏细胞单层培养物中荧光稳态各向异性随浴液中庚醇浓度增加而成比例降低的观察结果，进一步支持了这一假说。两种记录方法测得的单通道电导（γj）相同（分别为21和40 - 45 pS）；庚醇未改变γj。在庚醇诱导连接偶联降低的条件下，连接电导（gj）在对照条件下未观察到电压敏感性时，却表现出电压敏感性。这些结果表明，庚醇依赖性解偶联是由缝隙连接通道开放概率降低所致。
