Richardson R M, Goldstein M B, Stinebaugh B J, Halperin M L
J Lab Clin Med. 1979 Sep;94(3):510-8.
Rabbits normally excrete an alkaline urine, whereas rat urine is usually acidic. This study was designed to determine whether this difference was attributable to the composition of the diet or to specific metabolism of the species. Balance studies were performed in rabbits and rats with comparable growth rates who were consuming standard laboratory feed. The diets for both species had an excess of fixed cations over anions. Rats fed Rat Chow excreted urine containing net acid, whereas rabbits fed the same diet excreted urine containing net base. Rabbits eating Rabbit Chow excreted a very alkaline urine, but rats eating the same diet excreted much less alkali when expressed per kilogram of body weight. Balance studies demonstrated that rabbits absorbed a much higher proportion of dietary organic anions and excreted a larger fraction of this as total CO2. Collecting-duct hydrogen ion secretion and ammonium excretion, which are normally low in the rabbit during metabolic acidosis, were not increased when Rat Chow was consumed by rabbits for 2 weeks. In summary, feeding identical diets to rabbits or rats led to vastly different values for NAE. There appeared to be a gastrointestinal difference, as judged by the quantity of absorbed organic anions, as well as a metabolic difference reflected in the very different ratios of urinary total CO2 to organic anion.
兔子通常排出碱性尿液，而大鼠尿液通常呈酸性。本研究旨在确定这种差异是归因于饮食组成还是物种的特定代谢。对生长速率相当且食用标准实验室饲料的兔子和大鼠进行了平衡研究。两种物种的饮食中固定阳离子都超过阴离子。喂食大鼠饲料的大鼠排出含净酸的尿液，而喂食相同饮食的兔子排出含净碱的尿液。吃兔粮的兔子排出非常碱性的尿液，但吃相同饮食的大鼠按每千克体重计算排出的碱要少得多。平衡研究表明，兔子吸收了更高比例的膳食有机阴离子，并将其中更大一部分以总二氧化碳的形式排出。兔子在代谢性酸中毒期间通常较低的集合管氢离子分泌和铵排泄，在兔子食用大鼠饲料2周后并未增加。总之，给兔子或大鼠喂食相同的饮食会导致净酸排泄量有很大差异。从吸收的有机阴离子数量判断，似乎存在胃肠道差异，同时尿液总二氧化碳与有机阴离子的比例差异很大也反映出代谢差异。
