Approximations of kidney models and compartmental kidney models

Compartmental models were proposed in sixties to model the flow of isotopes through the kidney. These models were then criticized to not conform to the physiology of the kidney flow of isotopes. That is why they were abandoned, even thought their fits to the measured data were usually good. In this paper it is shown that some approximations of a physiological model proposed earlier by the present author can be interpreted as equations describing compartmental models. Their parameters have, however, different interpretation than the rates of intercompartmental flows. Diagrams of the time variations of the isotope content in the kidney are compared for the exact and approximate model using computer simulation technique