Influence of vitamin E administration on platelet functions in hormonal contraceptive users.

Platelet functions (aggregation, clotting activity), platelet lipid biosynthesis, sterol composition and phospholipid fatty acids were studied in relation to plasma lipids and fatty acids as well as dietary habits at day 5 and 21 of the menstrual cycle in 30 women having used hormonal contraceptive for several years. The women were studied again on day 21 of the second cycle after they had taken for two months 200 mg vitamin E per day in addition to the contraceptive. At day 21 (after 3 weeks of hormonal contraceptive) as compared to day 5, there was a significant increase in the clotting activity of platelets and the response to ADP-induced aggregation concomitant with a decrease in plasma vitamin E. After vitamin E administration, platelet activity at day 21 was markedly decreased, being similar to the activity at day 5, with a significant increase in the level of vitamin E in plasma and platelets. The high response of platelets to aggregation in women using contraceptives does not seem to be associated with the intake of saturated fat but rather with that of 18:2. The aggregation to thrombin was mostly related to lanosterol biosynthesis and the aggregation to ADP to platelet cholesterol, but not to plasma lipids or apoproteins. The present pilot study suggests that the platelet hyperactivity of long-term hormonal contraceptive users might be dependent upon a low level of platelet alpha-tocopherol which can be rapidly overcome by giving a supplement of vitamin E.