Younes H, Rémésy C, Behr S, Demigné C
Centre de Recherches en Nutrition Humaine de Clermont-Ferrand/Theix, Institut National de la Recherche Agronomique, St-Gènes-Champanelle, France.
Am J Physiol. 1997 Mar;272(3 Pt 1):G515-21. doi: 10.1152/ajpgi.1997.272.3.G515.
The influence of nondigestible carbohydrate on intestinal fermentations and on the route of nitrogen excretion has been investigated in normal rats and in unilaterally nephrectomized rats. Rats were adapted to 10% casein diets, either fiber free or containing different levels of two fermentable carbohydrates, inulin or crude potato starch. Ingestion of fermentable carbohydrate led to a considerable enlargement of the cecum because of hypertrophy of the cecal wall and an increase in cecal contents. Cecal digesta contained elevated concentrations of short-chain fatty acids, resulting in acidic pH. Diets containing fermentable carbohydrate enhanced fecal nitrogen excretion, which was more than doubled at the highest level of inulin or potato starch. In parallel, urinary nitrogen excretion was significantly decreased by fermentable carbohydrate. Although these changes were similar in all animals, there were quantitative differences in the response of nephrectomized animals to fermentable carbohydrate. In nephrectomized rats, plasma urea concentrations were more than 2.5 times higher than in normal rats (5.8 mM compared with 2.2 mM). Plasma urea concentrations were reduced by approximately 50% when normal rats were fed diets containing 7.5-15% inulin or 10-20% resistant starch. In nephrectomized animals fed the highest level of fermentable carbohydrate, plasma urea concentrations were also significantly decreased, but only by 30%. In nephrectomized rats, the concentration of nitrogen cycling in the cecum was greater (urea nitrogen transfer into the cecum was 50-60% greater and ammonia flux from the cecal lumen to the blood was two times higher than in normal rats), but fecal nitrogen excretion was equivalent in normal and nephrectomized animals. When expressed as a percentage of total nitrogen excretion, fecal nitrogen excretion was <20% in animals fed fiber-free diets, compared with 45-50% in normal animals and 40% in nephrectomized animals fed fermentable carbohydrate.
已在正常大鼠和单侧肾切除大鼠中研究了不可消化碳水化合物对肠道发酵及氮排泄途径的影响。大鼠适应了不含纤维或含有不同水平两种可发酵碳水化合物（菊粉或粗制马铃薯淀粉）的10%酪蛋白饮食。摄入可发酵碳水化合物导致盲肠因盲肠壁肥大和盲肠内容物增加而显著增大。盲肠消化物中短链脂肪酸浓度升高，导致pH值呈酸性。含可发酵碳水化合物的饮食增加了粪便氮排泄，在菊粉或马铃薯淀粉最高水平时，粪便氮排泄增加了一倍多。同时，可发酵碳水化合物使尿氮排泄显著减少。尽管所有动物的这些变化相似，但肾切除动物对可发酵碳水化合物的反应存在定量差异。在肾切除大鼠中，血浆尿素浓度比正常大鼠高2.5倍以上（分别为5.8 mM和2.2 mM）。当正常大鼠喂食含7.5 - 15%菊粉或10 - 20%抗性淀粉的饮食时，血浆尿素浓度降低了约50%。在喂食最高水平可发酵碳水化合物的肾切除动物中，血浆尿素浓度也显著降低，但仅降低了30%。在肾切除大鼠中，盲肠中的氮循环浓度更高（尿素氮向盲肠的转移比正常大鼠高50 - 60%，盲肠腔向血液的氨通量比正常大鼠高两倍），但正常动物和肾切除动物的粪便氮排泄量相当。以总氮排泄的百分比表示时，喂食无纤维饮食的动物粪便氮排泄量<20%，而正常动物为45 - 50%，喂食可发酵碳水化合物的肾切除动物为40%。
