Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907-2093, USA.
Anal Bioanal Chem. 2011 Feb;399(4):1613-22. doi: 10.1007/s00216-010-4454-5. Epub 2010 Dec 9.
Calcium-41 (t(1/2) = 10(5) years) can be used after a single dose to follow calcium metabolism over a subject's lifetime. The aims of this study were to expand a (41)Ca kinetic model and estimate bone resorption in women with stable bone loss, compare the rates with those calculated with classical isotope studies, and to use the model to simulate dynamic changes in urinary (41)Ca:Ca ratios and bone balance for the design and interpretation of (41)Ca studies. Forty-two women >5 years post-menopause were given (41)Ca intravenously. Bone mineral content and bone mineral density of total body were measured by dual-energy X-ray absorptiometry at the beginning of the study. Urine collections were made periodically for up to ~5 years while subjects were free living. Urinary (41)Ca:Ca ratios were measured using accelerator mass spectrometry. The isotope data were analyzed by compartmental modeling. Four compartments were necessary to fit the urinary tracer data and total bone calcium. The final model included pathways for absorption, distribution, urinary excretion, and endogenous excretion and was used to calculate rates of bone turnover. Estimates of bone resorption in a subset of the women (n = 13), studied previously in a 3-week balance and full kinetic study with (45)Ca, agreed with those using (41)Ca methodology. Thus, rates of bone resorption can be estimated from (41)Ca urinary data in stable post-menopausal women. The model was used to simulate dynamic changes in urinary (41)Ca:Ca ratios and bone balance, as a result of interventions that perturb calcium metabolism to aid in study design and interpretation.
钙-41（t(1/2) = 10(5) 年）可单次给药，用于追踪受试者一生中的钙代谢情况。本研究的目的是扩展（41）Ca 动力学模型并估计稳定骨质流失女性的骨吸收情况，比较这些与经典同位素研究计算的速率，并使用模型模拟尿液（41）Ca：Ca 比值和骨平衡的动态变化，以设计和解释（41）Ca 研究。42 名绝经后>5 年的女性接受静脉内（41）Ca 给药。在研究开始时，使用双能 X 射线吸收法测量全身骨矿物质含量和骨矿物质密度。在自由生活期间，定期采集尿液，持续时间长达~5 年。使用加速器质谱法测量尿液（41）Ca：Ca 比值。同位素数据通过室模型分析进行分析。需要四个室来拟合尿液示踪剂数据和总骨钙。最终模型包括吸收、分布、尿液排泄和内源性排泄途径，并用于计算骨转换率。在之前使用（45）Ca 进行了为期 3 周的平衡和完整动力学研究的女性亚组（n = 13）中，对一部分女性的骨吸收进行了估计，其结果与使用（41）Ca 方法学的结果一致。因此，稳定绝经后女性的骨吸收率可以从（41）Ca 尿数据中估计。该模型用于模拟尿液（41）Ca：Ca 比值和骨平衡的动态变化，作为干预钙代谢以帮助研究设计和解释的结果。
