Summary
The enhancement of the blood fibrinolytic potential by physical exercise is generally
attributed to the release of tissue-type plasminogen activator (t-PA) from the vessel
wall. In this study we have investigated the possible contribution of urokinase-type
plasminogen activator (u-PA).
Six healthy male volunteers (age 21–25 years) were screened for their ability to perform
maximal exercise for their age-group for 12 min on a bicycle ergometer. Subsequently,
on one occasion they were required to remain supine for 2 h (from 8.30 a. m. onwards)
and on another they performed maximal exercise (from 9.00 a.m. onwards). During exercise
an increase in u-PA antigen and plasmin-activatable pro-urokinase (proUK) activity,
concurrent with t-PA antigen and euglobulin t-PA activity, was observed in all six
volunteers, while at rest these parameters remained unaffected. Mean u-PA- and t-PA
antigen increased, respectively, from 4.2 ± 1.0 ng/ml and 5.8 ± 2.1 ng/ml before exercise
to 9.8 ± 3.0 ng/ml and 18.3 ± 3.8 ng/ml (peak). Mean plasminactivatable proUK activity
and t-PA activity increased, respectively, from 2.1 ± 0.4 ng/ml and 0.3 ± 0.2 ng/ml
before exercise to 4.3 ± 1.7 ng/ml and 7.2 ± 4.0 ng/ml (peak). The increases were
statistically significant throughout (paired t-test, pre vs post, antigen P <0.005
and activity P <0.02). After cessation of exercise u-PA and t-PA declined concurrently
to normal values with a 50"/" decay in about 5 min. In conclusion, we found that both
u-PA antigen and plasmin-activatable proUK activity are, concurrently with t-PA, enhanced
upon exercise and, therefore, we consider that u-PA also contributes to – and co-operates
in – the enhancement of the blood fibrinolytic potential and activity under these
conditions.
