[Effects of oral contraceptives on fibrinolytic system among Japanese and American women].

Neither urinary plasmin-activity nor whole plasmin changed during the menstrual period of healthy women. Among Japanese women, pill-takers' recorded a markedly higher level of plasmin-activity than non-takers. No such trend was observed with whole plasmin and FDP. Among American women, no significant difference between non-users and users concerning the levels of whole plasmin, plasmin activity and FDP was observed. Among Japanese women, a significantly high level of plasmin activity was observed after administering pills for one year. Five out of six rabbits treated with thrombin intramuscularly showed a level of urinary plasmin activity which is five times higher than the control. The number of platelets decreased in two rabbits, the amounts of fibrinogen in one, and prothrombin time in one. Plasmin activity did not change in rabbits treated with 1/20 X and 1 X maximal tolerated dose (MTD) of norethisterone and mestranol, but was significantly increased by 50 X MTD of norethisterone and mestranol. On the other hand, when treated with both norethisterone and mestranol, plasmin activity did not change with 1/20 X but significantly increased with 1 X and 50 X. The activity of plasminogen activator in glomeruli of rats was increased dose-dependently by thrombin. However, norethisterone, mestranol, and norethisterone-mestranol failed to activate production of plasminogen activator. In conclusion, looking at the comparison of the fibrinolytic system of American and Japanese women, the fibrinolytic system in endothelial cells was found to react well to thrombin among Japanese but weakly among Americans. The weak reaction of the fibrinolytic system among Americans is suggested to be a cause of the increase in thrombosis.