Andon M B, Kanerva R L, Schulte M C, Smith K T
Food and Beverage Technology Division, Procter and Gamble Company, Miami Valley Laboratories, Cincinnati, Ohio 45239-8707.
Am J Physiol. 1993 Oct;265(4 Pt 1):E554-8. doi: 10.1152/ajpendo.1993.265.4.E554.
In a longitudinal study we determined the effect of animal age as well as Ca source and radiolabeling method on Ca bioavailability by measuring whole body 47Ca retention (WBR) in male Sprague-Dawley rats. The WBR assay was performed without surgery or anesthesia, and the same groups of animals were studied at 8, 16, 20, and 32 wk of age. Rats were administered a 6-mg radiolabeled oral dose of Ca as Ca citrate malate (CCM) or intrinsically or extrinsically labeled CaCO3 or hydroxyapatite (HAP). Fractional Ca retention was measured from the 72-h postdose WBR divided by WBR at time 0. WBR was significantly affected by Ca source with CCM > CaCO3 > HAP at all ages (P < 0.001). The rank order and relative bioavailabilities of these Ca salts in the rat model agreed well with literature values for Ca absorption in adult humans. Although percent WBR decreased significantly with advancing age (P < 0.001), the mean rate of decline (-3.4%/wk) was not affected by Ca source. Extrinsic radiolabeling overestimated (approximately 20%) Ca bioavailability when the rats were young. However, the magnitude of this effect diminished with advancing animal age and was not significant across all ages (repeated measures analysis of variance P = 0.10).
在一项纵向研究中，我们通过测量雄性斯普拉格-道利大鼠的全身47Ca保留率（WBR），确定了动物年龄、钙源和放射性标记方法对钙生物利用度的影响。WBR测定在无手术或麻醉的情况下进行，对相同组别的动物在8、16、20和32周龄时进行研究。给大鼠口服6毫克放射性标记的钙，形式为柠檬酸苹果酸钙（CCM）、内源性或外源性标记的碳酸钙或羟基磷灰石（HAP）。钙分数保留率通过给药后72小时的WBR除以0时的WBR来测量。WBR受钙源的显著影响，在所有年龄组中CCM > 碳酸钙 > HAP（P < 0.001）。这些钙盐在大鼠模型中的排序和相对生物利用度与成年人类钙吸收的文献值非常吻合。尽管WBR百分比随年龄增长显著下降（P < 0.001），但下降的平均速率（-3.4%/周）不受钙源影响。当大鼠年轻时，外源性放射性标记高估了（约20%）钙的生物利用度。然而，这种影响的程度随着动物年龄的增长而减小，且在所有年龄组中不显著（重复测量方差分析P = 0.10）。
