Tissue distribution of vWF mRNA in murine tissues. Competitive RT-PCR was performed using 1 μg of RNA from each tissue and 1 × 10⁴ molecules of cRNA standard. The top band (1,130 bp) is the PCR product derived from the endogenous vWF mRNA and the bottom band (172 bp) is from the cRNA standard. The difference in the expression of vWF mRNA among murine tissues can be approximated by comparing the intensity of the endogenous mRNA bands.