Wilson H D, Schedl H P
Dig Dis Sci. 1981 Mar;26(3):237-41. doi: 10.1007/BF01391636.
To test the hypothesis that individual proteins have specific effects on calcium absorption, two proteins, casein and fibrin, were pair-fed in diets to rats for 3 weeks. Each protein was fed at normal (1.2%) and low (0.02%) calcium intakes. Diets were matched in other nutrients. Calcium absorption, measured in vitro as serosal-to-mucosal concentration ratio of 45Ca developed by duodenal sacs, was the same for both protein groups when calcium intake was normal and was increased by both low-calcium diets. Comparing low-calcium diets, absorption was greater in fibrin-fed than casein-fed groups. Balance studies showed that casein- and fibrin-fed rats taking normal calcium diets excreted the same amounts of calcium and phosphorus in urine and feces. Fibrin-fed rats taking low calcium excreted twice as much calcium as casein-fed rats and had decreased serum calcium. The balance data suggest that, compared to casein, fibrin prevents absorption or promotes excretion of calcium when calcium intake is low, and the response to calcium depletion is enhanced calcium absorption. It is concluded that individual proteins can alter calcium transport through effects on overall calcium homeostasis.
为了验证单个蛋白质对钙吸收有特定影响这一假设，将酪蛋白和纤维蛋白这两种蛋白质以配对喂养的方式加入大鼠日粮中，持续3周。每种蛋白质分别在正常钙摄入量（1.2%）和低钙摄入量（0.02%）的情况下进行喂养。日粮中的其他营养素保持一致。通过十二指肠囊测定的45Ca的浆膜与黏膜浓度比来体外测量钙吸收，结果显示当钙摄入量正常时，两个蛋白质组的钙吸收相同，且两种低钙日粮均能增加钙吸收。比较低钙日粮时，纤维蛋白喂养组的钙吸收高于酪蛋白喂养组。平衡研究表明，摄入正常钙日粮的酪蛋白和纤维蛋白喂养的大鼠在尿液和粪便中排出的钙和磷量相同。摄入低钙的纤维蛋白喂养大鼠排出的钙量是酪蛋白喂养大鼠的两倍，且血清钙降低。平衡数据表明，与酪蛋白相比，当钙摄入量低时，纤维蛋白会阻止钙的吸收或促进钙的排泄，而对钙缺乏的反应是增强钙吸收。得出的结论是，单个蛋白质可通过影响整体钙稳态来改变钙的转运。
