Summary

We examined the diurnal pattern in Plasminogen Activator Inhibitor-type 1 (PAI-1) activity and Plasminogen activator (t-PA) in relationto the 4G/5G-polymorphism in the promoter of the PAI-1 gene. Theanalyses were performed in the Arnhem Elderly Study, a population-basedstudy of 598 elderly. A single blood sample was drawn and thetime of blood sampling was recorded (between 8 a. m. and 5.30 p. m.).Plasma PAI-1 activity was strongly associated with time of bloodsampling, showing the highest values in the early morning. The diurnalpattern was clearly present in the 4G/4G (n = 184) and 4G/5G (n = 275)genotypes, but not in the 5G/5G-genotype (n = 139). T-PA antigenshowed a weak diurnal variation, which did not differ across thevariants of the 4G/5G-polymorphism. Our findings raise the hypothesisthat 5G-homozygotic persons may be relatively protected from diurnalvariation in the occurrence of coronary events.