Two compartment model with feedback control of precursor (pregnenolone) to cortisol and its adrenal secretion.
This two compartment model for substances, Q1 (precursor) and Q2 (cortisol) is simplified from the original models of Urquhart (1968) by Jacquez (1972). Precursor Q1 is formed at a rate inhibited by itself at higher concentrations. Its conversion to cortisol is stimulated by ACTH, a saturable process. Increases in ACTH deplete PREG concentration and increase the secretion from the adrenal.
Figure: (Top) Concentration response of cortisol and precursor to ACTH infusion. Q1 is concentration of precurosr in compartment 1 and Q2 is cortisol concentration in compartment 2. (Bottom) ACTH input as a function of time.
The equations for this model may be viewed by running the JSim model applet and clicking on the Source tab at the bottom left of JSim's Run Time graphical user interface. The equations are written in JSim's Mathematical Modeling Language (MML). See the Introduction to MML and the MML Reference Manual. Additional documentation for MML can be found by using the search option at the Physiome home page.
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Urquhart J and Li CC. The dynamics of adrenocortical secretion. Am J Physiol 214: 73-85, 1968. Jacquez JA. Compartmental analysis in biology and medicine. Kinetics of distribution of tracer-labeled materials. Amsterdam: Elsevier Publishing Co., 1972, pp.237 (See pp 213-216) Jacquez JA. Compartmental analysis in biology and medicine. 3rd ed.. Ann Arbor, MI: BioMedware, 1996, 514 pp.
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