Plasminogen activator inhibitor 1 expression in platelets is not influenced by the 4G/5G promoter polymorphism

In the present study we investigated the influence of the 4G/5G promoter polymorphism of the PAI-1 gene on the levels of PAI-1 mRNA and protein in platelets. After a screening of healthy male subjects, thirty-eight subjects homozygote for either the 4G or 5G allele were investigated. mRNA levels were quantified by real-time PCR and PAI-1 antigen in platelets and plasma was analysed by ELISA. The platelet PAI-1 mRNA levels correlated significantly with the PAI-1 antigen content, but there was no association between the polymorphism and mRNA levels, or protein levels in platelets. Also, plasma levels of PAI-1 antigen were not associated with homozygosity of the 4G/5G polymorphism, but as expected BMI and triglycerides emerged as significant predictors of plasma PAI-1 levels. The importance of the 4G/5G polymorphism on PAI-1 levels is controversial and the present study shows that although levels of platelet mRNA are related to its content of PAI-1 protein, there is no association between the 4G/5G promoter polymorphism and platelet PAI-1 mRNA or protein expression.