Buchowski M S, Sowizral K C, Lengemann F W, Van Campen D, Miller D D
Department of Food Science, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca 14853.
J Nutr. 1989 Feb;119(2):228-34. doi: 10.1093/jn/119.2.228.
Dairy products doubly labeled with 45Ca and 47Ca were used to evaluate an extrinsic labeling procedure for calcium bioavailability determination. Nonfat milk, yogurt, and fresh cheese curd were prepared from caprine milk that was intrinsically labeled with 45Ca. The products were then labeled extrinsically with 47Ca and administered to rats by gavage. The 47Ca to 45Ca ratio in bone and teeth averaged about 1.00 with either milk, yogurt, or CaCl2, but the ratio was about 1.04 when dosed with cheese curd. Ca absorption, determined by whole-body counting of 47Ca, was lower (P less than 0.05) in cheese curd (59%) than in either milk (69%), yogurt (72%), or CaCl2 (72%). Expressed as percent of dose, the absorption of 47Ca was highly correlated with bone 47Ca (r = 0.973) and with bone 45Ca (r = 0.946). Correlation between tibia 47Ca and tibia 45Ca was r = 0.923. For the dairy products tested, our results indicated that extrinsic 47Ca was absorbed similarly to intrinsic 45Ca. Moreover, the percent of radioactive dose retained in bone appears to be a valid indicator of relative bioavailability of food Ca.
用同时标记有45Ca和47Ca的乳制品来评估一种用于测定钙生物利用度的外源性标记程序。脱脂牛奶、酸奶和新鲜奶酪凝乳由用45Ca进行内源性标记的羊奶制成。然后用47Ca对这些产品进行外源性标记，并通过灌胃法给予大鼠。用牛奶、酸奶或氯化钙给药时，骨骼和牙齿中47Ca与45Ca的比率平均约为1.00，但用奶酪凝乳给药时该比率约为1.04。通过对47Ca进行全身计数测定的钙吸收，在奶酪凝乳中（59%）低于牛奶（69%）、酸奶（72%）或氯化钙（72%）（P小于0.05）。以剂量百分比表示，47Ca的吸收与骨骼中的47Ca（r = 0.973）和骨骼中的45Ca（r = 0.946）高度相关。胫骨中47Ca与胫骨中45Ca的相关性为r = 0.923。对于所测试的乳制品，我们的结果表明外源性47Ca的吸收与内源性45Ca相似。此外，保留在骨骼中的放射性剂量百分比似乎是食物钙相对生物利用度的有效指标。
