Spray D C, Harris A L, Bennett M V
J Gen Physiol. 1981 Jan;77(1):77-93. doi: 10.1085/jgp.77.1.77.
The conductance of junctions between amphibian blastomeres is strongly voltage dependent. Isolated pairs of blastomeres from embryos of Ambystoma mexicanum, Xenopus laevis, and Rana pipiens were voltage clamped, and junctional current was measured during transjunctional voltage steps. The steady-state junctional conductance decreases as a steep function of transjunctional voltage of either polarity. A voltage-insensitive conductance less than 5% of the maximum remains at large transjunctional voltages. Equal transjunctional voltages of opposite polarities produce equal conductance changes. The conductance is half maximal at a transjunctional voltage of approximately 15 mV. The junctional conductance is insensitive to the potential between the inside and outside of the cells. The changes in steady-state junctional conductance may be accurately modeled for voltages of each polarity as arising from a reversible two-state system in which voltage linearly affects the energy difference between states. The voltage sensitivity can be accounted for by the movement of about six electron charges through the transjunctional voltage. The changes in junctional conductance are not consistent with a current-controlled or ionic accumulation mechanism. We propose that the intramembrane particles that comprise gap junctions in early amphibian embryos are voltage-sensitive channels.
两栖类卵裂球之间连接的电导强烈依赖于电压。对美西钝口螈、非洲爪蟾和豹蛙胚胎分离出的成对卵裂球进行电压钳制，并在跨连接电压阶跃期间测量连接电流。稳态连接电导随着任何一种极性的跨连接电压急剧下降。在大的跨连接电压下，存在一个小于最大值5%的电压不敏感电导。相反极性的相等跨连接电压产生相等的电导变化。在大约15 mV的跨连接电压下，电导为最大值的一半。连接电导对细胞内外的电位不敏感。对于每种极性的电压，稳态连接电导的变化可以通过一个可逆的双态系统精确建模，其中电压线性影响状态之间的能量差。电压敏感性可以通过大约六个电子电荷通过跨连接电压的移动来解释。连接电导的变化与电流控制或离子积累机制不一致。我们提出，构成早期两栖类胚胎间隙连接的膜内颗粒是电压敏感通道。
