Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, USA.
Int J Vitam Nutr Res. 2014;84 Suppl 1:9-15. doi: 10.1024/0300-9831/a000181.
Isotope dilution methods have been successfully used to estimate vitamin A status in human populations as well as to evaluate the impact of vitamin A interventions. The most commonly applied isotope dilution method is the retinol isotope dilution technique, which is based on the 1989 "Olson equation" for estimating total body vitamin A stores (sometimes equated to liver vitamin A) after an oral dose of labeled vitamin A. The equation relies on several factors related to absorption and retention of the dose, the equilibration of label in plasma vs. liver, and timing of a blood sample for measurement of labeled vitamin A. Here, the assumptions underlying these factors are discussed, and new results based on applying model-based compartmental analysis [specifically, the Simulation, Analysis and Modeling software (WinSAAM)] to data on retinol kinetics in humans are summarized. A simplification of the Olson equation, in which plasma tracer is measured 3 days after administration of the oral dose and several factors are eliminated, is presented. The potential usefulness of the retinol isotope dilution technique for setting vitamin A requirements and assessing vitamin A status in children, as well as the confounding effects of inflammation and likely variability in vitamin A absorption, are also discussed.
同位素稀释法已成功用于评估人体维生素 A 状况以及评价维生素 A 干预措施的影响。最常用的同位素稀释法是视黄醇同位素稀释技术，该技术基于 1989 年“奥尔森方程”，用于估计口服标记维生素 A 后全身维生素 A 储存量（有时等同于肝脏维生素 A）。该方程依赖于与剂量吸收和保留相关的几个因素、血浆与肝脏中标记物的平衡以及用于测量标记维生素 A 的血液样本的时间。本文讨论了这些因素的假设，并根据应用基于模型的房室分析[具体为模拟、分析和建模软件（WinSAAM）]对人体视黄醇动力学数据的新结果进行了总结。提出了一种简化的奥尔森方程，其中在口服剂量给药后 3 天测量血浆示踪剂，并消除了几个因素。还讨论了视黄醇同位素稀释技术在确定维生素 A 需求和评估儿童维生素 A 状况方面的潜在用途，以及炎症的混杂影响和维生素 A 吸收的可能变异性。
