Stokke E S, Naess P A, Ostensen J
Institute for Experimental Medical Research, University of Oslo, Ullevål Hospital, Norway.
Scand J Clin Lab Invest. 1997 Oct;57(6):471-7. doi: 10.3109/00365519709084596.
Lithium clearance is often used as a marker for proximal tubular water transport. Proximal tubular transport may be modulated by changing plasma potassium concentration. The aim of the present study was to examine the effect of acute changes in plasma potassium concentration on proximal tubular fluid and lithium transport. Clearance studies were performed in seven anaesthetised, volume-expanded dogs treated with amiloride (1 mg kg-1 body weight) to block distal tubular potassium secretion, and with bumetanide (30 micrograms kg-1 body weight) to inhibit sodium reabsorption in Henle's loop. When plasma potassium concentration was raised from 2.6 +/- 0.2 to 7.9 +/- 0.2 mmol l-1, water reabsorption decreased from 23.9 +/- 2.9 to 19.8 +/- 2.2 ml min-1, whereas lithium reabsorption increased from 10.5 +/- 2.3 to 18.1 +/- 2.3 mumol min-1, at constant glomerular filtration rate. We conclude that acute elevation of plasma potassium concentration inhibits proximal tubular fluid reabsorption, but stimulates renal lithium reabsorption. Thus, lithium reabsorption cannot be used as a marker for proximal tubular transport during acute changes in plasma potassium concentration.
锂清除率常被用作近端肾小管水转运的标志物。近端肾小管转运可通过改变血浆钾浓度来调节。本研究的目的是检验血浆钾浓度急性变化对近端肾小管液和锂转运的影响。对7只麻醉的、血容量扩充的狗进行清除率研究，用氨氯吡咪（1毫克/千克体重）阻断远端肾小管钾分泌，并用布美他尼（30微克/千克体重）抑制亨氏袢的钠重吸收。当血浆钾浓度从2.6±0.2毫摩尔/升升至7.9±0.2毫摩尔/升时，在肾小球滤过率恒定的情况下，水重吸收从23.9±2.9毫升/分钟降至19.8±2.2毫升/分钟，而锂重吸收从10.5±2.3微摩尔/分钟增至18.1±2.3微摩尔/分钟。我们得出结论，血浆钾浓度急性升高会抑制近端肾小管液重吸收，但会刺激肾脏锂重吸收。因此，在血浆钾浓度急性变化期间，锂重吸收不能用作近端肾小管转运的标志物。
