Department of Physiology, University of Veterinary Medicine Hannover, Bischofsholer Damm 15, 30173 Hannover, Germany.
Domest Anim Endocrinol. 2010 Apr;38(3):190-9. doi: 10.1016/j.domaniend.2009.10.003. Epub 2009 Nov 25.
It was the aim of the present study to collect basic data on calcium (Ca) and phosphorus (P) homoeostasis in sheep. Two series of experiments were carried out to investigate the effects of 1,25-dihydroxyvitammin D(3) (calcitriol) in supraphysiological dosage in combination with varying alimentary Ca supply. In the first series, blood samples were collected over 72 h to determine the concentrations of total Ca (Ca), ionized Ca (Ca(2+)), inorganic phosphate (P(i)), and the bone resorption marker CrossLaps (CL). In the second series, measurements were carried out over 12h. In addition, urine samples were collected to calculate the fractional excretions (FE) of Ca and P(i). Changes in plasma macromineral concentrations (P<0.01) as well as in CL (P<0.001) and endogenous calcitriol (P<0.05) were observed in the alimentary Ca-restricted animals, indicating that the reduction of daily Ca intake challenged the animals' macromineral homeostatic mechanisms. However, the Ca-restricted diet had an effect on neither FE of Ca nor on FE of P(i). The treatment resulted in peak serum calcitriol concentrations between 1,900 and 2,500 pg/mL, and supraphysiological concentrations were maintained for the next 48 h. Irrespective of dietary Ca, calcitriol had hypercalcemic and hyperphosphatemic effects. An increase in CL was revealed only in the Ca-restricted, calcitriol-treated sheep (P<0.01), reflecting a remarkable enhancement of Ca mobilization from the bone by calcitriol exclusively in this group. From these data, it can be concluded that the sheep can be a suitable animal model for studying catabolic effects of Ca deficiency and calcitriol on bone metabolism.
本研究旨在收集绵羊钙（Ca）和磷（P）动态平衡的基础数据。进行了两个系列的实验，以研究超生理剂量的 1,25-二羟维生素 D3（骨化三醇）与不同饮食 Ca 供应相结合对 Ca 和 P 代谢的影响。在第一个系列中，采集了 72 小时的血样以确定总 Ca（Ca）、离子化 Ca（Ca2+）、无机磷（P(i)）和骨吸收标志物 CrossLaps（CL）的浓度。在第二个系列中，进行了 12 小时的测量。此外，收集了尿液样本以计算 Ca 和 P(i)的分数排泄率（FE）。饮食性 Ca 限制动物的血浆宏量矿物质浓度（P<0.01）、CL（P<0.001）和内源性骨化三醇（P<0.05）发生变化，表明每日 Ca 摄入量的减少挑战了动物的宏量矿物质稳态机制。然而，Ca 限制饮食对 Ca 的 FE 或 P(i)的 FE 没有影响。该治疗导致血清骨化三醇浓度峰值在 1900 到 2500 pg/mL 之间，并且在接下来的 48 小时内维持超生理浓度。无论饮食 Ca 如何，骨化三醇都具有升血钙和升血磷的作用。仅在 Ca 限制、骨化三醇治疗的绵羊中观察到 CL 的增加（P<0.01），这反映了骨化三醇仅在该组中显著增强了 Ca 从骨骼中的动员。从这些数据可以得出结论，绵羊可以成为研究 Ca 缺乏和骨化三醇对骨代谢的分解代谢作用的合适动物模型。
