Platelet production and survival in newborn vs adult mice. (A) Platelet survival was compared between neonatal (n = 16) and adult (n = 7) mice using in vivo biotinylation. Changes in total biotinylated platelets were expressed as percent of the value 24 hours postbiotinylation. (B) A dynamic mathematical model was designed to compute platelet production rate, using data from the same 16 newborn and 7 adult mice. The results of the model indicated that the platelet production rate (expressed as number of platelets/µL of blood/h) was similar in newborn and adult mice. (C) The model also indicated that the platelet lifespan of newborn mice was significantly longer than that of adult mice (4.9 ± 1.3 vs 3.9 ± 1.1 days; *P < .01). The differences disappeared as newborn mice reached day 14 (3.8 ± 1 day). Details of the model are provided in the supplemental Methods and supplemental Figure 2. (D) Platelet turnover was further analyzed following transfusion of CMFDA-labeled adult platelets into newborn (n = 9) and adult (n = 12) mice. Changes in the number of transfused platelets were expressed as percent of that at 2 minutes posttransfusion.