Comparison of Mpl levels in PLTs isolated from control, TPO^+/−, TPO^−/−, and TPO-stimulated thrombocythemic mice. Immunoblot analysis of platelet lysates from (A) TPO^+/− and TPO^−/− mice; (B) the two types of TPO-stimulated mice, using antibodies directed against Mpl, GpIIb, P-selectin, and actin. For ↑ PLT and ↑↑ PLT, see legend to Fig 3. Two independent lysates were used for each TPO stimulation model.