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The plasma-to-cell cycle of transferrin

Transferrin, biochemistry, physiology and clinical significance

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The quantitative determination of iron kinetics and hemoglobin synthesis in human subjects.

Publisher Summary This chapter discusses the occurrence of anemia in cancer. Many of the theories about the cause of anemia arose from early studies on leukemia. It is generally accepted that the anemia results from the invasion and crowding out of the bone marrow by neoplastic tissue, a theory sponsored by the eminent German hematologist, Pappenheim. The rapid introduction of radioisotope techniques is providing new tools, which promise to aid in a more quantitative evaluation of these various theories. The new information derived from such approaches has led, in many instances, to definite conclusions and increased understanding, and in others, to contradiction and variable data. Because the confusion can be traced in many instances to the use of techniques, which retain intrinsic defects, an attempt is made in the chapter to evaluate these techniques in some detail and to indicate their limitations and potentialities in the study of the anemia associated with cancer.

Anemia in cancer.

A method is presented for calculating internal iron kinetics. An early reflux associated with extravascular exchange and a late reflux associated with erythropoiesis are described. A biologic model of iron exchange is proposed in which erythron iron turnover is divided into an effective portion (iron fixed in circulating red cells) and wastage iron of erythropoiesis (late reflux). Nonerythroid iron exchange also has a fixed portion (parenchymal uptake) and an early reflux (lymphatic circuit), both of which correlate in amount with the amount of plasma iron. Ferrokinetic measurements in normal subjects and in various pathologic states are presented to validate the model.

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Ferrokinetics: a biologic model for plasma iron exchange in man

Transport iron normally exists in the plasma as ferric beta-l-globulinate. Since in most individuals the greater part of the body iron is incorporated in the hemoglobin of the red blood cells, it is probable that changes in the production and destruction of these erythrocytes will be reflected in the turnover of plasma iron. Radioactive iron of high specific activity is particularly useful for a study of iron metabolism since it can be injected intravenously in tracer amounts without changing the steady state of the organism; the turnover of this radioiron will then mirror the metabolism of the iron in the body.

/pdf/the-rate-of-removal-of-radioactive-iron-from-the-plasma-an-2ww30oqff6.pdf

The rate of removal of radioactive iron from the plasma—an index of erythropoiesis

Previous reports(1,2) concerning the disappearance of a tracer dose of radioactive iron from the plasma implied a single plasma iron pool with no significant return of radioiron to the plasma during the experimental period of one to 2 hours. Assuming instantaneous mixing following the injection of ferric 59-beta-1 globulinate, as well as a constant relative disappearance rate, the theoretical data could be represented by a single exponential function, i.e., a straight line on semi-log paper. Such a first approximation fitted the experimental data well because of the large errors involved in electroplating(123) and the relatively insensitive counting technics employed(123).Two considerations prompted reevaluation of the above concepts. Firstly, utilizing improved counting technics it was noted that the experimental data were no longer approximated by a straight line when plotted on semilog paper. Re-examination of some of the published data in earlier reports reveals similar findings(1,4). Secondly, the ap...

D. Leavitt

Papers

The rate of removal of radioactive iron from the plasma—an index of erythropoiesis

Pool systems in iron metabolism; with special reference to polycythemia vera.

Blood Exchange in Replacement Transfusions. II. Studies with Erythrocytes Tagged with Radioactive Phosphorus

Studies in iron kinetics. ii. interpretation of experimental data in terms of multiple pool systems.

Radioactive iron studies in anemia.