Armbrecht H J, Zenser T V, Gross C J, Davis B B
Am J Physiol. 1980 Nov;239(5):E322-7. doi: 10.1152/ajpendo.1980.239.5.E322.
The purpose of this study was to characterize the changes that take place in adaptation to chronic calcium (Ca) or phosphorus (P) restriction with age. Adaptation in male F344 rats aged 1.5, 3, 12, and 18 mo was studied by feeding rats either a low-Ca diet, a low-P diet, or a high-Ca-P diet for 14 days. Plasma Ca remained relatively constant with age, but plasma P markedly decreased between 3 and 12 mo regardless of diet. Intestinal adaptation was determined by measuring the active transport of Ca by the intestine and by measuring the production of vitamin D-dependent calcium-binder protein. There was significant intestinal adaptation to Ca or P restriction at 1.5 mo, but there was none thereafter because Ca transport declined rapidly with age regardless of diet. The kidney adapted to the low-P diet by significantly reducing P excretion at all ages. In rats on a low-P diet, there was an increase in urinary P, which was due to a decrease in the tubular reabsorption of P and a decrease in urinary Ca with age. These changes in adaptation may reflect a decrease in serum 1,25-dihydroxyvitamin D levels and an increase in parathyroid hormone levels with age.
本研究的目的是描述随着年龄增长，适应慢性钙（Ca）或磷（P）限制过程中发生的变化。通过给1.5、3、12和18月龄的雄性F344大鼠喂食低钙饮食、低磷饮食或高钙磷饮食14天，研究其适应性。血浆钙随年龄保持相对恒定，但无论饮食如何，血浆磷在3至12月龄之间显著下降。通过测量肠道对钙的主动转运以及测量维生素D依赖性钙结合蛋白的产生来确定肠道适应性。在1.5月龄时，肠道对钙或磷限制有显著适应性，但此后没有，因为无论饮食如何，钙转运随年龄迅速下降。肾脏通过在所有年龄段显著减少磷排泄来适应低磷饮食。在低磷饮食的大鼠中，尿磷增加，这是由于肾小管对磷的重吸收减少以及尿钙随年龄下降所致。这些适应性变化可能反映了随着年龄增长血清1,25 - 二羟基维生素D水平降低和甲状旁腺激素水平升高。
