Brand S C, Whittam R
Biochim Biophys Acta. 1985 May 30;845(2):139-50. doi: 10.1016/0167-4889(85)90170-3.
A study has been made with pig red blood cells of the activation of the sodium pump by internal and external cations. Cell Na and K concentrations were altered using a PCMBS cation loading procedure. The procedure was characterised for resultant ionic conditions, maintenance of ATP levels and fragility. The activation of the sodium pump by external K was measured in cells suspended in choline (Na-free) solutions. External Cs was used as a substitute for K and elicited lower rates of pump activity. Both the Vmax and apparent Km for 42K influx and 134Cs influx increased as internal Na concentration was raised (within the non-saturating range). Vmax/apparent Km ratios for cation influx were constant. Raising external Cs concentration exerted a similar influence on pump activation by internal Na: both the maximum pump velocity and the apparent Na-site dissociation constant (K'Na) increased. The results provide evidence for a transmembrane connection between cation binding sites on opposite faces of the membrane and are consistent with a consecutive model for the sodium pump in pig red blood cells.
已对猪红细胞中内外阳离子对钠泵的激活作用进行了研究。使用对氯汞苯甲酸阳离子加载程序改变细胞内钠和钾的浓度。该程序的特点是能产生特定的离子条件、维持三磷酸腺苷（ATP）水平并保持细胞脆性。在悬浮于胆碱（无钠）溶液中的细胞中测量了外部钾对钠泵的激活作用。使用外部铯作为钾的替代物，发现其引发的泵活性速率较低。随着细胞内钠浓度升高（在非饱和范围内），42K内流和134Cs内流的最大反应速度（Vmax）和表观米氏常数（Km）均增加。阳离子内流的Vmax/表观Km比值保持恒定。提高外部铯浓度对内部钠激活泵的作用产生类似影响：最大泵速和表观钠位点解离常数（K'Na）均增加。这些结果为膜相对两侧阳离子结合位点之间的跨膜连接提供了证据，并且与猪红细胞中钠泵的连续模型一致。
