Folkerd E, Singer D R, Cappuccio F P, Markandu N D, Sampson B, MacGregor G A
Department of Medicine, St. George's Hospital Medical School, London, United Kingdom.
Am J Physiol. 1995 Apr;268(4 Pt 2):F718-22. doi: 10.1152/ajprenal.1995.268.4.F718.
We compared endogenous with exogenous lithium clearance (CLi) and studied the effects of dietary salt intake on endogenous CLi in healthy volunteers. Lithium was detectable within a narrow fourfold range in serum and in urine in all 25 subjects studied [serum (n = 25), mean 0.27 +/- 0.02 mumol/l, range 0.13-0.55 mumol/l; urine (n = 20), range 1.49-7.32, mean 4.09 +/- 0.36 mumol/24 h]. Mean clearance and fractional excretion of endogenous lithium were lower (15.2 +/- 2.0 ml/min and 16.4 +/- 2.1%, respectively) compared with results obtained using the exogenous CLi technique (25.5 +/- 1.7 ml/min and 27.9 +/- 2.1%; P < 0.01 and P < 0.05, respectively; n = 17). In a separate group of six normal subjects, absolute (8.7 +/- 2.9 vs. 20.7 +/- 3.8 ml/min) and fractional excretion of lithium (8.3 +/- 2.9 vs. 18.0 +/- 5.1%) were significantly lower on 5 days of low (31 +/- 10 mmol/day) vs. high sodium intake (357 +/- 78 mmol/day; P < 0.05). Use of endogenous CLi precludes the need for lithium tablets. This could be a particular advantage in population studies and permits serial measurement of CLi on different days. Our results show that it is important to take dietary sodium intake into account in studies of endogenous CLi. Lower values for endogenous compared with exogenous CLi could reflect differences in renal handling depending on the plasma lithium concentration. This clearly requires further study.
我们比较了内源性与外源性锂清除率（CLi），并研究了饮食中盐摄入量对健康志愿者内源性CLi的影响。在所有25名研究对象的血清和尿液中，锂的检测范围很窄，为四倍[血清（n = 25），平均0.27±0.02 μmol/l，范围0.13 - 0.55 μmol/l；尿液（n = 20），范围1.49 - 7.32，平均4.09±0.36 μmol/24小时]。与使用外源性CLi技术获得的结果相比，内源性锂的平均清除率和分数排泄较低（分别为15.2±2.0 ml/分钟和16.4±2.1%）（25.5±1.7 ml/分钟和27.9±2.1%；P < 0.01和P < 0.05，分别；n = 17）。在另一组6名正常受试者中，低钠摄入（31±10 mmol/天）5天与高钠摄入（357±78 mmol/天）相比，锂的绝对清除率（8.7±2.9对20.7±3.8 ml/分钟）和分数排泄（8.3±2.9对18.0±5.1%）显著降低（P < 0.05）。使用内源性CLi无需服用锂片。这在人群研究中可能是一个特别的优势，并允许在不同日期对CLi进行连续测量。我们的结果表明，在研究内源性CLi时考虑饮食中钠的摄入量很重要。与外源性CLi相比，内源性CLi值较低可能反映了根据血浆锂浓度肾脏处理方式的差异。这显然需要进一步研究。
