Sjodin R A, Beaugé L A
J Gen Physiol. 1968 Sep;52(3):389-407. doi: 10.1085/jgp.52.3.389.
"Low sodium" muscles were prepared which contained around 5 mmoles/kg fiber of intracellular sodium. "High sodium" muscles containing between 15 and 30 mmoles/kg fiber of intracellular sodium were also prepared. In low sodium muscles application of 10(-5)M strophanthidin reduced potassium influx by about 5%. Potassium efflux was unaffected by strophanthidin under these conditions. In high sodium muscles, 10(-5)M strophanthidin reduced potassium influx by 45% and increased potassium efflux by 70%, on the average. In low sodium muscles sodium efflux was reduced by 25% during application of 10(-5)M strophanthidin while in high sodium muscles similarly treated, sodium efflux was reduced by about 60%. Low sodium muscles showed a large reduction in sodium efflux when sodium ions in the Ringer solution were replaced by lithium ions. The average reduction in sodium efflux was 4.5-fold. Of the amount of sodium efflux remaining in lithium. Ringer's solution, 40% could be inhibited by application of 10(-5)M strophanthidin. The total sodium efflux from low sodium muscles exposed to Ringer's solution in which lithium had been substituted for sodium ions for a period of 1 hr can be fractionated as 78% Na-for-Na interchange, 10% strophanthidin-sensitive sodium pump, and 12% residual sodium efflux. It is concluded that large strophanthidin-sensitive components of sodium and potassium flux can be expected only at elevated sodium concentrations within the muscle cells.
制备了“低钠”肌肉，其细胞内钠含量约为5毫摩尔/千克纤维。还制备了“高钠”肌肉，其细胞内钠含量在15至30毫摩尔/千克纤维之间。在低钠肌肉中，施加10⁻⁵M毒毛花苷可使钾离子内流减少约5%。在这些条件下，毒毛花苷对钾离子外流没有影响。在高钠肌肉中，10⁻⁵M毒毛花苷平均使钾离子内流减少45%，使钾离子外流增加70%。在低钠肌肉中，施加10⁻⁵M毒毛花苷时，钠离子外流减少25%；而在同样处理的高钠肌肉中，钠离子外流减少约60%。当任氏溶液中的钠离子被锂离子取代时，低钠肌肉的钠离子外流大幅减少。钠离子外流的平均减少倍数为4.5倍。在锂任氏溶液中剩余的钠离子外流中，40%可被施加10⁻⁵M毒毛花苷所抑制。暴露于钠离子被锂离子取代1小时的任氏溶液中的低钠肌肉的总钠离子外流可分为78%的钠-钠交换、10%的毒毛花苷敏感钠泵和12%的残余钠离子外流。得出的结论是，只有在肌肉细胞内钠浓度升高时，才可能出现大量对毒毛花苷敏感的钠和钾通量成分。
