Modeling of platelet kinetics in a subject receiving bolus PEG-rHuMGDF on day 1 and autologous¹¹¹In-labeled platelets on day 8 and day 18. (A) Model prediction (solid line) of platelet response to PEG-rHuMGDF is overlaid on observed platelet counts (closed circles). (B) Model prediction (solid line) of platelet tracer kinetics during nonsteady state conditions are overlaid on observed¹¹¹In-labeled platelet activities (closed squares). (C) Theoretical time course (solid line) of mean peripheral platelet age after transient stimulation of megakaryocytopoiesis explains the alteration in the platelet tracer profile on day 18 relative to day 8. Model parameters: S₀, 93 300 platelets per day; k_mpl, 1 030 000 platelets/d/(ng/mL); γ, 1.0; τ_m, 5.16 days; V_p, 6200 mL; Λ, 10.3 days; k_ρ, 7700 platelets/μL/d.