[The study on the platelet aggregation inhibition activity of placental brush border (the mechanism of platelet aggregation inhibition)].

To clarify the role of placental brush border in the regulation of placental microcirculation, we investigated the platelet aggregation inhibition activity of placental brush border membrane vesicles (BBMV) and obtained the following results. 1. There was very strong platelet aggregation inhibiting activity in placental BBMV. In the 20-40 micrograms/ml protein concentration, the BBMV almost completely inhibited the platelet aggregation induced by ADP, arachidonic acid and collagen, and in the 100-150 micrograms/ml protein concentration, the BBMV almost completely inhibited the platelet aggregation induced by ristocetin. 2. There existed a very strong ADP degrading activity (ADPase activity) in the placental BBMV. The platelet aggregation activity of ADP was completely lost when ADP was preincubated with the placental BBMV. 3. The placental BBMV inhibited platelet malondialdehyde (MDA) production. With the 20 micrograms/ml and 100 micrograms/ml protein concentrations of placental BBMV, 22% and 65% of platelet MDA production was inhibited respectively.