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. Author manuscript; available in PMC: 2010 Jun 15.
Published in final edited form as: Toxicol Appl Pharmacol. 2009 Apr 14;237(3):345–356. doi: 10.1016/j.taap.2009.04.005

Figure 8.

Figure 8

Simulations demonstrating that homeostatic control mediated by negative feedback alone cannot generate steady-state hormesis (A), but may generate conditioning hormesis involving two sequential dosing events (B). The dose response curves for X′ vs Xext were obtained at 66 h, 2 h after the onset of the second dose (downward arrow). The results were obtained from simulations with the phase II negative feedback enabled, and the phase I negative feedback and phase I to II feedforward disabled. Disabling phase I negative feedback and phase I to II feedforward was implemented by setting CYP at a fixed concentration at 1.5 μM, and setting the initial concentrations of DRE(Nrf2), DRE(GST), DRE(MRP), and DRE(CYP) all to zero.