For each tissue and organ modeled in the chemokinetic model, the cytodynamic model calculates quantitatively the carcinogenic and/or cytotoxic effects of the pollutant in the corresponding tissue or organ. The approach adopted is an extension of the Armitage-Doll model of carcinogenesis and follows the cytodynamic model as outlined, for example, in [7, 3]. Note that this type of model is able to handle hormetic behavior of a tissue to an outside response, a feature of strong interests to toxicologists . The modeler has to specify the number of different cell populations per compartment that should be modeled. The dynamic behavior of each population is then governed by the pollutant concentration inside the compartment (by a toxic or a mutagenic effect) and by the population numbers of the other cell types. The governing ordinary differential equations, however, can not be classified according to some simple criterion. As a consequence, the user must specify the right hand side of the equations explicitly in the source code by modifying the subroutine CMPCLLR (file compartment.f) accordingly.
The solver routine for the nonlinear system of ordinary differential equations is fully integrated into the routine for solving the chemokinetical equations described in the last chapter.
We describe some simple examples for the type of cytodynamic activity which can be modeled by this approach.