Morihata H, Kawawaki J, Sakai H, Sawada M, Tsutada T, Kuno M
Department of Physiology, Osaka City University Medical School, Abeno-ku, Osaka 545-8585, Japan.
Neurosci Res. 2000 Nov;38(3):265-71. doi: 10.1016/s0168-0102(00)00170-x.
Voltage-gated proton (H(+)) channels are unique mechanisms to extrude a massive amount of H(+), and are proposed to regulate intracellular pH of microglia during respiratory bursts. Temporal variations of the H(+) current were studied in rat spinal microglia cultivated on the glial cell layer using the voltage-ramp protocol. Repetitive applications of the large and long-lasting depolarization decreased the amplitudes of the H(+) current transiently and reversibly. This decrease was accompanied by a shift of the reversal potential to a more positive direction, indicating that a drop in the transmembrane pH gradient (delta pH) by the H(+) efflux through the channel reduced the current. The decline of the H(+) current during depolarizations was also observed in a rat microglial cell line (GMI-R1). An increase in the extracellular buffer suppressed the reduction of the current, suggesting that H(+) secreted into the extracellular space contributed to the drop in delta pH. On the other hand, the amplitudes of the H(+) current often fluctuated greatly at intervals of 5-20 min without changes in delta pH. These results suggest that the H(+) current of microglia is tuned via both delta pH-dependent and -independent mechanisms, which may regulate both microglial behavior and the pH environments of the surrounding neural tissue.
电压门控质子（H⁺）通道是大量排出H⁺的独特机制，有人提出在呼吸爆发期间它可调节小胶质细胞的细胞内pH值。使用电压斜坡方案，研究了在胶质细胞层上培养的大鼠脊髓小胶质细胞中H⁺电流的时间变化。重复施加大的、持久的去极化会使H⁺电流的幅度暂时且可逆地降低。这种降低伴随着反转电位向更正的方向移动，表明通过通道外流的H⁺导致跨膜pH梯度（ΔpH）下降，从而使电流减小。在大鼠小胶质细胞系（GMI-R1）中也观察到去极化期间H⁺电流的下降。细胞外缓冲液的增加抑制了电流的降低，表明分泌到细胞外空间的H⁺导致了ΔpH的下降。另一方面，H⁺电流的幅度常常每隔5 - 20分钟就会大幅波动，而ΔpH并无变化。这些结果表明，小胶质细胞的H⁺电流是通过依赖和不依赖ΔpH的机制进行调节的，这可能同时调节小胶质细胞的行为和周围神经组织的pH环境。
