FIBRINOLYTIC FACTORS ASSOCIATE WITH MAXIMAL OXYGEN UPTAKE AND HDL SUBFRACTIONS IN MEN 547

The relations of tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor (PAI) to cardiorespiratory fitness and high-density lipoprotein (HDL) subclasses were examined in 150 men aged 52 to 62 years. PAI activity was analyzed by a chromogenic assay, and tPA activity bioimmunologically. Total HDL was fractionated into three subclasses by density gradient ultracentrifugation, and concentrations of cholesterol, phospholipids, cholesterol esters and triglycerides were measured in each fraction. Maximal oxygen uptake (˙VO2max) was assessed by analyzing respiratory gases during a maximal exercise test. The mean (95%CI) tPA activity was 0.46 (0.42;0.50) IU · ml-1, PAI activity 19.4(17.5;21.3) AU · ml-1, total HDL cholesterol 43 (41;45) mg· dl-1 and ˙VO2max 30.6 (29.4;31.7) ml · kg-1 · min-1. ˙VO2max associated with PAI (r=-0.352, p<0.001) and tPA activities (r=0.31, p<0.001). PAI (r=-0.31 to -0.42) and tPA activities (r=0.37 to 0.47) were associated with total HDL, HDL2b and HDL2a cholesterol, cholesterol esters and phospholipids (p<0.001 for all), but not with these components in HDL3 subfraction. PAI (r=-0.20, p=0.014) and tPA (r=0.25, p=0.002) correlated with triglycerides in HDL2b, while PAI was directly and tPA inversely related (p<0.001 for both) to triglycerides in HDL3 subfraction. When age, ˙VO2max, sum of skinfolds, HDL2b cholesterol and HDL2b triglycerides were entered in multiple stepwise regression analyses, HDL2b cholesterol and ˙VO2max explained 20% of the variance in PAI activity. In the same model, HDL2b cholesterol, ˙VO2max and age explained 27% of the variance in tPA activity. In summary, tPA and PAI activities were mainly associated with larger than HDL2a particles, which are hypothesised to be more antiatherogenic than HDL3 subclass. Moreover, relation of cardiorespiratory fitness to fibrinolytic factors seem to be independent of plasma HDL.