Pool Systems in Iron Metabolism;with Special Reference to Polycythemia Vera. ∗

Abstract

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( 1 2 3 ) and the relatively insensitive counting technics employed( 1 2 3 ).

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 application of the previous approach to cases of polycythemia vera led to excessively high hemoglobin renewal rates and consequent shortened red cell survival times( 1 ). These findings were not in accord with data obtained by other methods( 5 6 7 ), nor with present basic concepts of the patho-physiology of this disorder( 8 ). It will be demonstrated that the experimental data can be more closely approximated by the sum of 2 exponential functions, thus requiring a more complex system than the one-pool model implied by the single exponential function.

Fig. 1a represents experimental data from a case of polycythemia vera plotted on a semilog scale, for the first hour of Fe⁵⁹ disappearance from the plasma.