- On 20 Jan 2005 at 16:58:56, "Jose Cortinas" (jose.cortinas.-a-.luc.ac.be) sent the message

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Dear All,

I have a question related to PK modeling.

I am recently working with PK models. Now I am studying the

"ELIMINATION OF PHOSPHATE DURING HEMODIALYSIS". I found an article

by Spalding,Chamney and Farrington (2002).

They did something similar and they propose 3 models based on 2, 3 and

4 compartments. In their article they

present the differential equations. The three models are bellow:

Model A: Passive diffusion

dCi=(Ci-Ce)Kie

--- ----------

dt Vi

dCe=(Ci-Ce)Kie - CeKd - CeQu

--- ------------------------

dt Ve

dVe=Qu

---

dt

Model B: Passive Diffusion + regulated intracellular phosphate

They assumed that from the third compartment the flux (F3) is:

F3 = (Ci - Ciset) G3

Ciset: desired set point

Thus the differential equation for the extracellular compartment needs

to be modified and it is

dCe=(Ci-Ce)Kie - CeKd - CeQu + F3

--- -----------------------------

dt Ve

Model C:

Passive Diffusion + regulated intracellular + immediate action

Consider an aditional mechanism that is invoked when phosphate falls

bellow a critical level

If Ci < Cicrit AND F4 off, then F4 on

If Cicrit < Ci < Cihighlimit AND F4 on, then F4 off

My question is the following. I would like to use this model, but I

would like to have the solutions for this equation for the 3 models, if

someone can help me I will appreciate it very much.

Thanks in advance,

Jose Cortinas Abrahantes

jose.cortinas.-at-.luc.ac.be

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