Sex-related differences in plasminogen activator and plasminogen activator inhibiting activities in young and aged rats.

The purpose of this study was to determine whether aging influences the sex-related differences in fibrinolytic activity in rats. We measured plasminogen activator (PA) activity and plasminogen activator inhibiting (PAI) activity in 5-, 12-, 45-, and 60-week-old male and female rats. We also examined the effects of gonadectomy and sex hormone-treatments in adult male and female rats. The increase in age did not influence the PA activity in the male or female rats. However, the PA activity was higher in the female rats than in the males in all four age groups. Orchidectomy caused a significant increase in PA activity in the male rats. Estradiol treatment induced a significant increase of PA activity in ovariectomized female rats. Testosterone treatment resulted in a decrease of PA activity in orchiectomized male rats. The increase in age had an effect on PAI activity; the activity level in the 45- and 60-week-olds was stronger than that in the 12-week-old rats. The PAI activity was not significantly different between the normal rats of each sex. Gonadectomy did not influence the PAI activity in male or female rats, and testosterone and estradiol treatments also did not affect PAI activity in gonadectomized male and female rats. We found that the increase in age induced a decrease in the fibrinolytic system in the rats, and that there were sex-related differences in the fibrinolytic system in even 60-week-old rats.