THE USE OF CR-51 AS A DIETARY MARKER IN RATS FOR THE DETERMINATION OFFE-59 ABSORBABILITY IN TERMS OF MUCOSAL UPTAKE AND MUCOSAL TRANSFER OF FE-59

The use of (CrCl3)-Cr-51 as a non-absorbable dietary marker for the de termination of mucosal uptake and transfer of Fe-59 ascorbate has been investigated in rats. In order to be useful, this marker has to satis fy two properties. Firstly, the gastrointestinal transit times of Cr-5 1 and Fe-59 have to be similar, and secondly, Cr-51 absorption has to be low, and independent of the diet to which it is added. We tested th ese prerequisites by determination of the isotope ratios in faecal sam ples, and Cr-51 retention in rats that were fed either a control diet, or a diet that was supplemented with ascorbic acid or phytate, which are thought to affect Cr-51 absorption. The study found similar faecal Cr-51/Fe-59 ratios for day 1 and 2 versus day 3. Cr-51 retention aver aged 3.14 %, and was independent of the diet. It is concluded that thi s double-isotope in vivo method is suitable for the determination of i ron absorption in terms of mucosal uptake and mucosal transfer in rats , and that it may be a useful alternative for current in vivo methods that can be applied only within terminal animal experiments.