Bond J H, Levitt M D
Gastroenterology. 1976 Jun;70(6):1058-62.
The quantity of lactose not absorbed by 4 normal and 6 lactase-deficient subjects was determined by three indirect methods which involved: (1) measurement of pulmonary hydrogen (H2) excretion, (2) pulmonary (14)CO2 excretion, and (3) stool (14)C excretion, after ingestion of 12.5 g of 1-(14)C-lactose and 4 g of polyethylene glycol (PEG). Results were compared with absorption determined directly from the (14)C:PEG ratio of multiple terminal ileal aspirates. The fraction of lactose not absorbed determined by ileal aspiration ranged from 0 to 8% in normals and 42 to 75% in mild-intolerant subjects. Whereas all three indirect methods were useful in qualitatively separating normal from deficient subjects, the quantity of lactose absorbed as determined by H2 excretion correlated most closely with ileal measurements (r = 0.94). Pulmonary (14)CO2 excretion for 24 hr after (14)C-lactose ingestion did not distinguish normal (17 +/- 4% (SEM) of ingested (14)C per 24 hr) from lactase-deficient subjects (21.1 +/- 3%). Likewise, stool (14)C:PEG ratios grossly underestimated malabsorption with less than one-quarter of the nonabsorbed (14)C appearing in the stool. This study suggests that individual differences in susceptibility to diarrhea after milk ingestion by lactase-deficient subjects may be due to differences in the quantity of lactose not absorbed and/or differences in the rate of bacterial metabolism of lactose in the colon. Analysis of ileal fluid collected during passage of the lactose meal indicated that about two-thirds of the osmotic load delivered to the colon consists of endogenous electrolytes. Thus the water load delivered to the colon is about 3 times that calculated to be osmotically held by the nonabsorbed sugar.
通过三种间接方法测定了4名正常受试者和6名乳糖酶缺乏受试者未吸收的乳糖量，这三种方法包括：（1）摄入12.5 g 1-（14）C-乳糖和4 g聚乙二醇（PEG）后，测量呼出氢气（H2）量；（2）测量呼出（14）CO2量；（3）测量粪便中（14）C排泄量。将结果与通过多次回肠末端抽吸物的（14）C:PEG比值直接测定的吸收情况进行比较。通过回肠抽吸测定的未吸收乳糖分数在正常受试者中为0至8%，在轻度不耐受受试者中为42至75%。虽然所有三种间接方法在定性区分正常受试者和缺乏受试者方面都很有用，但通过呼出氢气量测定的乳糖吸收量与回肠测量结果相关性最密切（r = 0.94）。摄入（14）C-乳糖后24小时呼出的（14）CO2量无法区分正常受试者（每24小时摄入的（14）C的17±4%（SEM））和乳糖酶缺乏受试者（21.1±3%）。同样，粪便（14）C:PEG比值严重低估了吸收不良情况，粪便中出现的未吸收（14）C不到四分之一。这项研究表明，乳糖酶缺乏受试者摄入牛奶后腹泻易感性的个体差异可能是由于未吸收乳糖量的差异和/或结肠中乳糖细菌代谢速率的差异。对乳糖餐通过期间收集的回肠液分析表明，输送到结肠的渗透负荷约三分之二由内源性电解质组成。因此，输送到结肠的水负荷约为未吸收糖渗透压保留量计算值的3倍。
