McKinney L C, Gallin E K
Department of Physiology, Armed Forces Radiobiology Research Institute, Bethesda, Maryland 20814.
J Membr Biol. 1990 Jun;116(1):47-56. doi: 10.1007/BF01871671.
The effects of adherence, cell morphology, and lipopolysaccharide on electrical membrane properties and on the expression of the inwardly rectifying K conductance in J774.1 cells were investigated. Whole-cell inwardly rectifying K currents (Ki), membrane capacitance (Cm), and membrane potential (Vm) were measured using the patch-clamp technique. Specific Ki conductance (GKi, whole-cell Ki conductance corrected for leak and normalized to membrane capacitance) was measured as a function of time after adherence, and was found to increase almost twofold one day after plating. Membrane potential (Vm) also increased from -42 +/- 4 mV (n = 32) to -58 +/- 2 mV (n = 47) over the same time period. GKi and Vm were correlated with each other; GL (leak conductance normalized to membrane capacitance) and Vm were not. The magnitudes of GKi and Vm 15 min to 2 hr after adherence were unaffected by the presence of 100 microM cycloheximide, but the increase in GKi and Vm that normally occurred between 2 and 8 hr after adherence was abolished by cycloheximide treatment. Membrane properties were analyzed as a function of cell morphology, by dividing cells into three categories ranging from small round cells to large, extremely spread cells. The capacitance of spread cells increased more than twofold within one day after adherence, which indicates that spread cells inserted new membrane. Spread cells had more negative resting membrane potentials than round cells, but GKi and GL were not significantly different. Lipopolysaccharide-(LPS; 1 or 10 micrograms/ml) treated cells showed increased Cm compared to control cells plated for comparable times. In contrast to the effect of adherence, LPS-treated cells exhibited a significantly lower GKi than control cells, indicating that the additional membrane did not have as high a density of functional GKi channels. We conclude that both adherence and LPS treatment increase the total surface membrane area of J774 cells and change the density of Ki channels. In addition, this study demonstrates that membrane area and density of Ki channels can vary independently of one another.
研究了黏附、细胞形态和脂多糖对J774.1细胞电膜特性及内向整流钾电导表达的影响。采用膜片钳技术测量全细胞内向整流钾电流（Ki）、膜电容（Cm）和膜电位（Vm）。特异性Ki电导（GKi，全细胞Ki电导经漏电校正并归一化至膜电容）作为黏附后时间的函数进行测量，发现接种一天后增加了近两倍。在同一时间段内，膜电位（Vm）也从-42±4 mV（n = 32）增加到-58±2 mV（n = 47）。GKi和Vm相互相关；GL（归一化至膜电容的漏电导）和Vm则不相关。黏附后15分钟至2小时，GKi和Vm的大小不受100μM环己酰亚胺存在的影响，但黏附后2至8小时通常发生的GKi和Vm增加被环己酰亚胺处理所消除。通过将细胞分为从小圆形细胞到大型、极度铺展细胞的三类，分析膜特性作为细胞形态的函数。铺展细胞的电容在黏附后一天内增加了两倍多，这表明铺展细胞插入了新的膜。铺展细胞的静息膜电位比圆形细胞更负，但GKi和GL没有显著差异。与培养相同时间的对照细胞相比，脂多糖-（LPS；1或10μg/ml）处理的细胞显示Cm增加。与黏附的影响相反，LPS处理的细胞表现出比对照细胞显著更低的GKi，表明额外的膜没有同样高密度的功能性GKi通道。我们得出结论，黏附和LPS处理均增加了J774细胞的总表面膜面积并改变了Ki通道的密度。此外，本研究表明膜面积和Ki通道密度可以相互独立地变化。
