Modeling of platelet kinetics in a subject receiving bolus PEG-rHuMGDF on day 1 and autologous¹¹¹In-labeled platelets at baseline and day 12. (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 12 relative to baseline. Model parameters: S₀, 53 100 platelets per day; k_mpl, 956 000 platelets/d/(ng/mL); γ, 1.0; τ_m, 5.13 days; V_p, 7700 mL; Λ, 9.70 days; k_ρ, 8000 platelets/μL/d.