The relative degradation rate of platelet PAI-1 mRNA in comparison to the 2 endogenous reference genes, GAPDH and cyclophilin. mRNA extracted from platelets incubated 0, 3, 8, and 24 hours was determined by real-time PCR. The degradation rate of PAI-1 mRNA was 4-fold higher than that of GAPDH and 8-fold higher than that of cyclophilin.