Clearance rate and production of platelets is increased in Pak2-null mice. (A) Quantification of in vivo biotinylated platelets 24, 48, 72, and 96 hours after N-hydroxysulfosuccinimidobiotin-biotin injection. Data expressed as percentage of baseline (24 hours postinjection; n = 4-8 mice/genotype per time point; mean ± SEM). (B) Quantification of the percentage of new, reticulated platelets as a percentage of total platelets (n > 5; mean ± SEM), 10 DPI. (C) MPV of Pak2^+/+ and Pak2^−/− platelets, 14 DPI. (D) Representative images of hematoxylin and eosin stained spleen sections from Pak2^+/+ and Pak2^−/− mice 14 DPI. Arrows indicate splenic megakaryocytes. Scale bar = 50 μm (40× original magnification). (E) Quantification of megakaryocytes in spleen sections counted in 10 low-power fields. (F) Spleen weight (mg) 14 DPI. All data from at least 3 mice/genotype; mean ± SEM. *P < .05.