Shibata K, Matsuo H
Department of Food Science and Nutrition, Teikoku Women's University, Osaka, Japan.
J Nutr. 1990 Oct;120(10):1191-7. doi: 10.1093/jn/120.10.1191.
We previously found that the sum total urinary excretion of nicotinamide and its metabolites in growing rats did not increase as the level of dietary casein increased. So, we investigated how the urinary excretion of nicotinamide and its metabolites changed when rats were fed nicotinic acid-free diets containing 10, 20 or 40% casein, or when they were fed diets containing nicotinic acid and the same level of protein but different levels of tryptophan. The latter diets were 10% casein-30% gelatin, 20% casein-20% gelatin or 40% casein. With the nicotinic acid-free diets, the sum total urinary excretion of nicotinamide and its metabolites was almost the same in the groups fed the 20 and 40% casein diets; however, it was significantly lower in the group fed the 10% casein diet. With diets containing the same level of protein, the sum total urinary excretion of these compounds in the groups fed the 10% casein-30% gelatin, 20% casein-20% gelatin and 40% casein diets were about 5, 7 and 11 mumol/d, respectively, values that were significantly different from each other. Therefore, it was found that only when the total protein intake was constant did the sum total urinary excretion of nicotinamide and its metabolites increase with increasing intake of tryptophan.
我们之前发现，在生长大鼠中，烟酰胺及其代谢产物的尿排泄总量并不会随着日粮酪蛋白水平的升高而增加。因此，我们研究了给大鼠喂食含10%、20%或40%酪蛋白的无烟酸日粮时，或者给它们喂食含烟酸且蛋白质水平相同但色氨酸水平不同的日粮时，烟酰胺及其代谢产物的尿排泄量是如何变化的。后一种日粮分别是10%酪蛋白-30%明胶、20%酪蛋白-20%明胶或40%酪蛋白。对于无烟酸日粮，在喂食20%和40%酪蛋白日粮的组中，烟酰胺及其代谢产物的尿排泄总量几乎相同；然而，在喂食10%酪蛋白日粮的组中，该值显著较低。对于蛋白质水平相同的日粮，在喂食10%酪蛋白-30%明胶、20%酪蛋白-20%明胶和40%酪蛋白日粮的组中，这些化合物的尿排泄总量分别约为5、7和11 μmol/d，这些值彼此之间存在显著差异。因此，发现只有当总蛋白质摄入量恒定时，烟酰胺及其代谢产物的尿排泄总量才会随着色氨酸摄入量的增加而增加。
