Armbrecht H J
Biochim Biophys Acta. 1986 Jul 16;882(3):281-6. doi: 10.1016/0304-4165(86)90249-7.
The purpose of these experiments was to determine whether there are changes in intestinal Ca and P uptake with age and whether the regulation of Ca and P uptake changes with age. Experiments were performed in male Fischer 344 rats aged 2-3 months (young), 12-14 months (adult) and 22-24 months (old). Ca and P uptake were measured simultaneously by incubating everted intestinal sacs in a buffered salt solution containing radiolabeled 0.25 mM Ca and 1.0 mM P for 15 min. Ca uptake declined by over 50% with age in the duodenum, and P uptake showed a similar decline in both the duodenum and jejunum. The biggest decrease was seen between the young and adult age groups. These decreases in uptake were paralleled by decreases in serum 1,25-dihydroxyvitamin D with age. Administration of 1,25-dihydroxyvitamin D-3 increased Ca uptake by 50-65% in the duodenum and increased P uptake by 85-120% in the duodenum and jejunum of both young and adult rats. Although 1,25-dihydroxyvitamin D-3 increased uptake by about the same percentage in each age group, the maximal uptake was much greater in the young than in the adult. Feeding a low-Ca diet increased duodenal Ca uptake by 68% and increased serum 1,25-dihydroxyvitamin D over 2-fold in young rats. There was no significant increase in either parameter in adult rats fed a low-Ca diet. However, duodenal P uptake was stimulated by a low-Ca diet by 87% in young rats and by 51% in adult rats. These results demonstrate that there is an age-related decline in Ca and P uptake by the intestinal mucosa. In addition, there is decreased capacity of 1,25-dihydroxyvitamin D-3 and a low-Ca diet to stimulate intestinal uptake in the adult.
这些实验的目的是确定肠道钙和磷的吸收是否随年龄变化，以及钙和磷吸收的调节是否随年龄改变。实验选用了2 - 3个月大（年轻）、12 - 14个月大（成年）和22 - 24个月大（老年）的雄性Fischer 344大鼠。通过将外翻肠囊置于含有放射性标记的0.25 mM钙和1.0 mM磷的缓冲盐溶液中孵育15分钟，同时测量钙和磷的吸收。随着年龄增长，十二指肠的钙吸收下降超过50%，十二指肠和空肠的磷吸收也呈现类似下降。在年轻组和成年组之间下降最为明显。吸收的这些下降与血清1,25 - 二羟维生素D随年龄的下降平行。给予1,25 - 二羟维生素D - 3可使年轻和成年大鼠十二指肠的钙吸收增加50 - 65%，十二指肠和空肠的磷吸收增加85 - 120%。尽管1,25 - 二羟维生素D - 3在每个年龄组增加吸收的百分比大致相同，但年轻组的最大吸收量比成年组大得多。给年轻大鼠喂食低钙饮食可使十二指肠钙吸收增加68%，血清1,25 - 二羟维生素D增加超过2倍。给成年大鼠喂食低钙饮食，这两个参数均无显著增加。然而，低钙饮食可刺激年轻大鼠十二指肠磷吸收增加87%，成年大鼠增加51%。这些结果表明，肠道黏膜对钙和磷的吸收存在与年龄相关的下降。此外，成年大鼠中1,25 - 二羟维生素D - 3和低钙饮食刺激肠道吸收的能力下降。
