| Abstract | 生体にとって重要な成分である鉄の吸収動態については, 放射性鉄の応用が容易になるにつれて多数の研究が行なわれ, 多くの新しい知見がえられるようになった. 経口的に投与された鉄の吸収率を測定する方法はいろいろあり, それぞれ利点および欠点を有しているが, いずれの方法を採用するかは, 研究の目的に応じ, またどのような装置を利用できるかによって決定されねばならない. 本論文では51Crで標識したCr2O3と, 59Feで標識した試料とを混合したのち経口投与し, 51Cr2O3がnon absorbable markerであることを利用して, 回収した糞便中の59Feと51Crの放射活性の比より, 鉄吸収率を測定する方法について検討を加えた. まずこの方法について, 基礎的検討を加え, 次に他の鉄吸収率測定法による値と比較し, 更に本法の臨床的応用について実験を行ない, 且つ考察を加えた. |
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| Abstract | [Summary] In order to determine the percentage of iron adsorption simply and accuraterly, carrier iron labelled with 59Fe after mixing with 51Cr2O3 as non absorbable marker was administered orally, and fecal collection was performed until less than 0.5% of the administered dose was present in a 24 hour specimen. By comparing the radioactivity ratio of the two isotopes between the standard sample and fecal specimen, per cent of iron excretion was determined, from which per cent of iron absorption was calculated. As preliminary experiment, 50 ml aqueous solution of 1 mg Cr2O3 labelled with 51Cr was administered orally to several control patients, and total body counting wss followed up, confirming no retention of 51Cr activity in the body, during which all urines were also cellected, revealing also no evidence of 51Cr activity. If carrier iron was as equal as about 40 mg, (in this report, ferrous sulfate was used as aqueous solution) , the appearance and disappearance of radioactivivity of 59Fe and 51Cr in the feces were almost in the same course, and 59Fe/51Cr in the feces was fairly constant, which negligible slow excretion of iron. Thus the 59Fe/51Cr in all collected feces was almost same to that of the two radioisotopes in their maximal excretion. Therefore iron absorption ratio could be determined by only measuring 59Fe/51Cr in their maximal excretion. To put it more concretely, water was added to each feces to a definite weight, and after being completely homogenized by mixer, a small portion of homogenous fecal solution was taken into a test tube, and the radioactivity of 59Fe and 51Cr was measured. There was no significant difference in the 59Fe/51Cr between samples with and without mixing. From these observations, it is possible to determine the per cent of iron absorption by a simple method for standard test : 40 mg of 59Fe labelled iron solution and 1 mg of 51Cr2O3 with 100 mg of ascorbic acid are simultaneously administered orally, and the feces in their maximal excretion is subjected to assay for 59Fe and 51Cr. This simple excretion ratio method was compared with three other methods-i.e. 1) Red cell radioiron method as a measure of iron absorption, 2) Double isotope method (Saylor-Finch's method) , 3) Whole body counting. There was close correlation among all, and the nearest close relation between the simple excretion ratio method and whole body counting, which is considered theoretically most accurate. As the general tendency, however, the method of red cell radioiron showed the lowest value as a measure of iron adsorption, then, Saylor-Finch's method, total body counting, and the simple excretion ratio method followed in this order. The ressons for these tendencieis are probably due to the following possibilities ; 1) tissue iron deposit after iron turnover, 2) hepatic iron deposit during first pass from the portal vein into the liver when fairly great amount of iron is absorbed, 3) natural slough of the intestinal mucosal cell which may still contain a small amount of radioiron, 4) a very slight quantity of gastrointestinal bleeding. This excretion ratio method revealed excellency in determing iron absorption. Moreover, this method gave us more rapid result than other methods, and was applicable to the serial determination within short period for clinical investigation of iron absorption even during oral iron therapy. |
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