Effect Of Aspirin On The Production Of PGI2 By Various Blood Vessels And Mda By Platelets

This study was desinged to determine whether the differential inhibition of prostacyclin(PGI2) production by vessel wall and malondialdehyde(MDA) production by platelet might be possible by oral administration of aspirin(ASA). Rabbits weghing 2-3kg were used. MDA production by platelet was measured by the Stuart’s method with minor modification. The PGI2 production by vessel wall was assessed by the Moncada’s method with minor modification.The PGI2 production by caval vein, pulmonary artery, pulmonary vein,femoral artery, femoral vein and coronary artery was 148±55%, 136±56%, 153±55%, 134±56%, 123±64%, 103±55% to that of aorta, respectively. The PGI2 production by these vessels was inhibited to 20-40% to their initial level 6h after the single oral administration of 0.3g ASA, and restored to the initial level by 24h, while the MDA production was inhibited more conspicuously and remained at less than 50% of the initial level even 48h.The effect of daily oral administration of ASA on production of PGI2 by aorta and MDA by platelet was investigated. PGI2 production was suppressed to about 10% of the initial level 24h after the last dose of 3 to 7 daily administration of 0,3g of ASA. This indicates that the daily ASA administration results in the cummulative inhibition of PGI2 production. On the other hand, when administered every other day, the same amount of ASA exerted significantly less inhibition of PGI2 production, being at about 50% of initial level 24h after the last dose. MDA production was nearly completely inhibited over the observation periods.These results suggests that the differential inhibition of vascular PGI2 production and platelet aggregation may be possible by the administration of ASA at an appropriate amount and proper interval.