Funaba M, Kawashima T, Yano H, Kawashima R
Department of Animal Science, Faculty of Agriculture, Kyoto University, Japan.
J Nutr Sci Vitaminol (Tokyo). 1990 Dec;36(6):559-67. doi: 10.3177/jnsv.36.559.
The effects of a high protein diet on bone formation and calcium (Ca) metabolism were evaluated in rats using an ectopic endochondral bone induction model. A control diet (18% casein) or a high protein diet (18% casein + 20% lactalbumin) was given to 50-day-old rats. Ten days after the feeding of the experimental diet, rats were intramuscularly implanted with demineralized bone powder (day 0). On day 14 and day 21, the implanted bone powder was harvested, and blood and urine samples were also obtained. Urinary Ca excretion was not increased on day 12-14; however, it was elevated on day 19-21 in rats fed the high protein diet compared with rats fed the control diet. The high protein diet remarkably stimulated urinary sulfate excretion in both sampling periods, which reflected dietary sulfur-containing amino acids contents. Also, rats fed the high protein diet exhibited a decrease in serum Ca concentrations. There was little difference in Ca contents and the activities of alkaline phosphatase and acid phosphatase in the implants between control group and high protein diet group on day 14 and day 21. Histological examination in the implanted demineralized bone powder on day 14 indicated only cartilage in rats fed the high protein diet in contrast to the occurrences of osteogenesis and remodeling in those fed the control diet. Retarded bone formation in rats fed the high protein diet might be owing to, in part at least, a restricted amount of Ca utilized at the stage of cartilage calcification.
使用异位软骨内骨诱导模型在大鼠中评估高蛋白饮食对骨形成和钙（Ca）代谢的影响。给50日龄的大鼠喂食对照饮食（18%酪蛋白）或高蛋白饮食（18%酪蛋白+20%乳白蛋白）。在喂食实验饮食10天后，给大鼠肌肉内植入脱矿骨粉（第0天）。在第14天和第21天，收集植入的骨粉，并采集血液和尿液样本。在第12 - 14天，高蛋白饮食组大鼠的尿钙排泄没有增加；然而，与喂食对照饮食的大鼠相比，在第19 - 21天，高蛋白饮食组大鼠的尿钙排泄升高。在两个采样期，高蛋白饮食均显著刺激尿硫酸盐排泄，这反映了饮食中含硫氨基酸的含量。此外，喂食高蛋白饮食的大鼠血清钙浓度降低。在第14天和第21天，对照组和高蛋白饮食组植入物中的钙含量以及碱性磷酸酶和酸性磷酸酶的活性几乎没有差异。在第14天对植入的脱矿骨粉进行组织学检查发现，与喂食对照饮食的大鼠出现骨生成和重塑相反，喂食高蛋白饮食的大鼠只有软骨。喂食高蛋白饮食的大鼠骨形成延迟可能至少部分归因于软骨钙化阶段钙利用量受限。
