Fermentable carbohydrate exerts a urea lowering effect in normals and nephrectomized rats. Younes, Hassan, Christian Remesy, Stephen Behrmdsu, and Christian Demigne. Laboratoire des maladies m[acute]etaboliques et des Micronutriments, I.N.R.A., Centre de Recherches en Nutrition Humaine de Clermont-Ferrand/Theix, F-63122 St-Gen[grave]es-Champanelle, France, Tel: (33) 73 62 42 33, Fax: (33) 73 62 46 38
APStracts 3:0229G, 1996.
The influence of non-digestible carbohydrate on intestinal fermentations and on the route of nitrogen (N) excretion has been investigated in normal rats and in unilateral 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. Feeding fermentable carbohydrate led to a considerable enlargement of the cecum due to a 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 conditions. Diets containing fermentable carbohydrate enhanced fecal N excretion, which was more than doubled at the highest level of inulin or potato starch. In parallel, urinary N 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 concentration was more than 2.5 times higher than in normal rats (5.8 mM compared to 2.2 mM). Plasma urea concentration was reduced by about 50% when normal rats were fed diets containing 7.5% to 15% inulin or 10% to 20% resistant starch. In nephrectomized animals fed the highest level of fermentable carbohydrate, plasma urea concentration was also significantly decreased, but only by 30%. In nephrectomized rats, N cycling in the cecum was increased (urea N 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 N excretion was equivalent in normal and nephrectomized animals. When expressed as a percentage of total N excretion, fecal N excretion was less than 20% in animals fed fiber-free diets, compared to 45-50% in normal animals and 40% in nephrectomized animals fed fermentable carbohydrate. 

Received 31 May 1996; accepted in final form 26 September 1996.
APS Manuscript Number G216-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996