Schwartz R, Belko A Z, Wien E M
J Nutr. 1982 Mar;112(3):497-504. doi: 10.1093/jn/112.3.497.
The primary purpose for the in vitro system described here was to provide an alternative method to intrinsic isotopic labeling for determining exchangeability of intrinsic food mineral with extrinsic inorganic mineral or one of its isotopes. In this system, foods or food mixtures extrinsically tagged with an isotope of the mineral of interest are incubated successively in media simulating peptic or pancreatic digestion. Radioactivity and mineral measurements are made on a)the mixture before digestion and after b)peptic and c)successive peptic pancreatic (P-Pa) digestion. Exchangeability is determined by comparing the specific activity in the peptic and P-Pa digest supernatants to that in the mixture before digestion. In addition, determination of the total soluble mineral after P-Pa digestion provides a measurement of potential bioavailability. The procedure was tested for calcium (Ca) exchangeability and bioavailability from a number of foods and food combinations with 45Ca as the tracer. It could be used for any mineral, however, including non-nutrient or toxic elements. It is likely to be most useful in association with human studies carried out with extrinsic stable (non-radioactive) or short-lived radioactive isotopes that are unsuitable for intrinsic labeling.
本文所述体外系统的主要目的是提供一种替代固有同位素标记的方法，用于确定食物中固有矿物质与外源无机矿物质或其同位素之一的交换性。在该系统中，用感兴趣的矿物质的同位素进行外源标记的食物或食物混合物，先后在模拟胃蛋白酶或胰酶消化的培养基中孵育。分别对a)消化前的混合物、b)胃蛋白酶消化后的混合物以及c)连续进行胃蛋白酶和胰酶（P-Pa）消化后的混合物进行放射性和矿物质测量。通过比较胃蛋白酶和P-Pa消化上清液中的比活度与消化前混合物中的比活度来确定交换性。此外，P-Pa消化后总可溶性矿物质的测定提供了潜在生物利用度的测量值。该方法以45Ca作为示踪剂，对多种食物和食物组合的钙（Ca）交换性和生物利用度进行了测试。然而，它可用于任何矿物质，包括非营养元素或有毒元素。与使用不适用于固有标记的外源稳定（非放射性）或短寿命放射性同位素进行的人体研究相结合时，它可能最有用。
