Agostini L, Down P F, Murison J, Wrong O M
Gut. 1972 Nov;13(11):859-66. doi: 10.1136/gut.13.11.859.
The effect of lactulose on faecal pH and ammonia has been studied in three normal subjects with the aid of dialysis of faeces in vivo. Observations were also made with sodium sulphate and the two hexahydric alcohols, mannitol and sorbitol, given in doses sufficient to cause a similar increase in stool weight. All four cathartics rendered the stool more acid, but there was no increase in the concentration of faecal ammonia. Lactulose, despite increasing faecal volume, did not cause an increase in the absolute amount of ammonia lost in the faeces, but the other purgatives did show a modest rise. The results are inconsistent with the theory that lactulose benefits the clinical picture of portosystemic encephalopathy by trapping ammonia in an acid stool. An alternative suggestion is advanced, namely, that any cathartic (including lactulose) reduces ammonia absorption from the colon by decreasing colonic transit time, and so reducing the amount of ammonia generated by autolysis of colonic bacteria.
借助体内粪便透析法，在三名正常受试者身上研究了乳果糖对粪便pH值和氨的影响。还对硫酸钠以及两种六元醇（甘露醇和山梨醇）进行了观察，给予的剂量足以使粪便重量有类似增加。所有这四种泻药都使粪便更偏酸性，但粪便氨浓度没有增加。尽管乳果糖增加了粪便体积，但并未导致粪便中氨流失的绝对量增加，而其他泻药确实有适度增加。这些结果与乳果糖通过在酸性粪便中捕获氨而改善门体性脑病临床症状的理论不一致。提出了另一种观点，即任何泻药（包括乳果糖）都通过缩短结肠转运时间来减少结肠对氨的吸收，从而减少结肠细菌自溶产生的氨量。
