Lemann J, Hornick L J, Pleuss J A, Gray R W
Department of Medicine, Medical College of Wisconsin, Froedtert Memorial Lutheran Hospital, Milwaukee 53226.
Clin Chem. 1989 Oct;35(10):2107-10.
We compared measurements of daily urine oxalate excretion in urines collected at the prevailing urine pH with measurements of urine oxalate excretion in urines collected into 20 mL of 6 mol/L HCl. We studied eight healthy adults fed constant diets. Urines were collected during control conditions and, in each subject, during the administration of NaCl, KCl, NaHCO3, or KHCO3, 90 mmol/day. Daily urine oxalate excretion calculated for collections made in acid averaged 271 (SD 79) mumol/day and did not vary with any of the salt supplements. When urines were collected at ambient urine pH (average 5.94, SD 0.23) during control conditions, and during the administration of NaCl or KCl, urine oxalate excretion averaged 263 (SD 88) mumol/day, a value not different from that for collections in acid. However, when urine was collected with no pH adjustment during NaHCO3 or KHCO3 administration (average pH 6.90, SD 0.14), apparent urine oxalate excretion averaged 398 (SD 132) mumol/day, significantly (P less than 0.025) exceeding the mean observed when urines were collected in acid. Moreover, the percentage increase in apparent oxalate excretion increased with urinary pH. These observations reinforce recommendations that urine specimens for measurement of oxalate be collected in acid to avoid the increase in apparent oxalate content that occurs during collection of alkaline urines. This increase presumably results from the well-known in vitro nonenzymatic conversion of ascorbate to oxalate.
我们将在尿液自然pH值下收集的尿液中每日草酸排泄量的测量值与收集到20 mL 6 mol/L盐酸中的尿液中草酸排泄量的测量值进行了比较。我们研究了8名食用固定饮食的健康成年人。在对照条件下以及在每名受试者服用90 mmol/天的氯化钠、氯化钾、碳酸氢钠或碳酸氢钾期间收集尿液。按在酸性条件下收集的尿液计算，每日草酸排泄量平均为271（标准差79）μmol/天，且不随任何一种盐补充剂而变化。在对照条件下以及在服用氯化钠或氯化钾期间，当在尿液自然pH值（平均5.94，标准差0.23）下收集尿液时，草酸排泄量平均为263（标准差88）μmol/天，这一数值与在酸性条件下收集的尿液的数值无差异。然而，在服用碳酸氢钠或碳酸氢钾期间（平均pH 6.90，标准差0.14）未进行pH调节收集尿液时，表观草酸排泄量平均为398（标准差132）μmol/天，显著（P<0.025）超过在酸性条件下收集尿液时观察到的平均值。此外，表观草酸排泄量的增加百分比随尿液pH值升高而增加。这些观察结果强化了以下建议：用于测量草酸的尿液标本应在酸性条件下收集，以避免在收集碱性尿液期间出现的表观草酸盐含量增加。这种增加可能是由于众所周知的体外抗坏血酸非酶促转化为草酸盐所致。
