STUDIES OF IODOALBUMIN METABOLISM. I. A MATHEMATICAL APPROACH TO THE KINETICS*

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Abstract
Tracer experiments employing Il31-iodoalbumin in human subjects indicated a kinetic system of at least 3 exchanging and 3 ancillary compartments. The analysis of the plasma and urine data from one thorough tracer study is presented in detail. The general solution of a 3-compartment open system is given along with modifications allowing solution of a 6-compartment system of the type indicated by the data. A procedure for evaluating the in-formation content of tracer data is given. A mapping procedure pre-serving the invariants of the data is presented and its value in delineating mathematically compatible and physically realizable models as well as the limits of computed turnover rates for non-unique solutions is illustrated. The solution is further developed to permit evaluation of the inequalities of final specific activities in the compartments of an open system and to allow the quantitation of errors in commonly used approximation methods. The analysis, when applied to iodoalbumin tracer data, showed the parallel model to be one of an infinite number of mathematically compatible and physically realizable models, while the series model was excluded. The analysis suggested that a rapidly exchanging extravascular compartment is the principal site of iodoalbumin degradation, irrespective of the model chosen.