Adaptation of middle aged rats to long-term restriction of dietary vitamin D and calcium.
Adaptation of middle aged rats to long-term restriction of dietary vitamin D and calcium.
复制标题
中年大鼠对长期限制膳食维生素 D 和钙的适应。
DOI：
10.1016/0003-9861(85)90231-0
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发表时间：
1985
影响因子：
3.9
通讯作者：
Forte,LR
中科院分区：
文献类型：
--
作者：
Armbrecht,HJ;Forte,LR
以前的研究表明，短期(4周)饮食维生素D和钙限制不会增加中年大鼠肾脏1，25-二羟基维生素D3(1，25(OH)2D3)的生成。本文报道的实验目的是确定中年大鼠是否表现出对长期限制饮食钙和维生素D的适应，并将这种适应与年轻大鼠的适应进行比较。中年(14-16个月)Fischer 344只大鼠分别饲喂0.02%钙缺乏维生素D(限食)和1.2%钙充足维生素D(对照)饲料。分别于1.5、3.0、4.5、6.0个月后处死各组大鼠。在离体肾皮质切片上测定了25(OH)D3向1，25(OH)2D3和24，25(OH)2D3的转化。限制组大鼠肾脏1，25(OH)2D3的生成量直到3个月才显著增加，4.5个月时最高可达对照组的85%。肾脏24，25(OH)2D3的产量仅在禁食1.5个月后显著降低，3.0个月时最大降幅达70%。两种饮食组的血钙均维持在11-12 mg/100ml之间，限食组血清免疫反应性甲状旁腺素(IPTH)较对照组略有升高1-2倍。相比之下，喂养1个月的幼鼠(3月龄)肾脏1，25(OH)2D3的产生增加了4倍，24，25(OH)2D3的产生减少了71%。喂养不足的饮食还导致血清钙降低43%，血清iPTH增加13倍。这些发现表明，中年大鼠确实改变了他们的25(OH)D代谢，以回应长期的维生素D和钙限制。然而，与幼鼠相比，反应的速度和幅度都有所降低。中年大鼠对维生素D的这种钝化反应反映了血清钙没有下降，而血清iPTH在维生素D和钙限制的反应中略有增加。
Previous studies have shown that middle aged rats do not increase renal 1,25-dihydroxyvitamin D3(1,25(OH)2D3) production in response to short-term (4 weeks) dietary vitamin D and calcium restriction. The purpose of the experiments reported here was to determine if middle aged rats demonstrate adaptation to long-term restriction of dietary calcium and vitamin D and to compare that adaptation to the adaptation seen in young rats. Middle aged (14–16 months) Fischer 344 rats were fed either a 0.02% calcium, vitamin D-deficient (restricted) or a 1.2% calcium, vitamin D-replete (control) diet. Rats from each group were sacrificed after 1.5, 3.0, 4.5, and 6.0 months on the diets. Renal conversion of 25(OH)D3to 1,25(OH)2D3and 24,25(OH)2D3was measuredin vitrousing isolated renal cortical slices. Renal 1,25(OH)2D3production in the restricted group was not significantly increased until 3 months and reached a maximum of 85% higher than the control at 4.5 months. Renal 24,25(OH)2D3production was significantly decreased after only 1.5 months of restriction and was decreased maximally by 70% at 3.0 months. Serum calcium remained in the range 11–12 mg/100 ml in both diet groups, and serum immunoreactive PTH (iPTH) was modestly increased one- to twofold in the restricted group compared to the control group. In contrast, young rats (3 months old) fed the deficient diet for 1 month had a fourfold increase in renal 1,25(OH)2D3production and a 71% decrease in 24,25(OH)2D3production. Feeding the deficient diet also produced a 43% reduction in serum calcium and a 13-fold increase in serum iPTH. These findings demonstrate that middle aged rats do alter their 25(OH)D metabolism in response to long-term vitamin D and calcium restriction. However, both the rapidity and the magnitude of the response is decreased compared to that seen in the young rat. This blunted vitamin D response in the middle aged rat reflects the lack of a decrease in serum calcium and the marginal increase in serum iPTH in response to vitamin D and calcium restriction.