Abstract
The purpose of this study was to determine whether aging influences sex-related differences in plasmin and plasmin-inhibiting activities in rats. We measured plasmin activity and plasmininhibiting activity in 5-, 12-, 45-, and 60-week-old male and female rats; and we also examined the effects of a gonadectomy and sex hormone treatments in adult male and female rats. The present study showed that the plasmin activity was higher in male rats than in females in all four age groups, which confirmed our previous findings. However, there was no significant sex-related difference in plasmin-inhibiting activity among the four age groups. An increase in age induced a decrease in plasmin activity and plasmin-inhibiting activity in both male and female rats. An ovariectomy significantly boosted plasmin and plasmin-inhibiting activity in female rats. Estradiol treatment induced a decrease in plasmin activity of orchiectomized male and ovariectomized female rats, and the plasmininhibiting activity of ovariectomized female rats. However, an orchiectomy slightly boosted plasmininhibiting activity in male rats. Testosterone treatment, on the other hand, did not significantly influence plasmin activity and plasmin-inhibiting activity in orchiectomized male and ovariectomized female rats.
It is suggested that estrogen regulates the system of plasmin and plasmin-inhibiting activities in rats, and a decrease of the plasmin and plasmin-inhibiting activities in aged rats is one of the reasons for more frequent thrombotic formation in aged rats.
