Measurement of thrombomodulin mRNA expression in brain capillaries by polymerase chain reaction.

Thrombomodulin (TM), an endothelial integral membrane protein, is a potent activator of the protein C anticoagulant pathway. TM protein expression is limited and regionally distributed in the brain. Recent investigations have demonstrated low TM mRNA expression by brain endothelium, corresponding to its distribution at the protein level. To facilitate the study of TM expression at the transcriptional level, we measured TM mRNA by quantitative-competitive polymerase chain reaction (QC-PCR) and by standard densitometric analysis of reverse transcriptase-PCR products (RT-PCR) in different regions of bovine brain. QC-PCR demonstrated differential TM mRNA expression in the pons (100+/-9%), cerebellum (359+/-103%), and cortex (441+/-24%). We compared these results with those of RT-PCR and found similar differences in relative TM mRNA expression in the pons (100+/-44%), cerebellum (343+/-8%), and cortex (404+/-62%). Data derived by QC-PCR and RT-PCR were highly correlated (r=0.99, p<0.03). These findings indicate that either QC-PCR or RT-PCR can be used to accurately quantify TM mRNA.