Many reports have been published on the role of platelets in thrombogenesis. The balance between TX A
2, produced from C
20:4 liberated from platelets, and PGI
2, derived from the blood vessel wall, is considered to be important from the viewpoint of fatty acid metabolism. We investigated platelet agglutination and the ratio of TX B
2 to 6-keto-PGF
1α to find a correlation between both prostanoids in patients with ischemic heart diseases. The ratio of TX B
2 to 6-keto-PGF
1α was found to be especially high in angina and A. M. I. This suggests that the metabolic production of C
20:4 and PGs from platelets may be accelerated in patients with ischemic heart diseases and that TX A
2 may be related to the severity of the disease.
In the present study, we used 3 agents with different mechanisms of action. A 300mg daily dose of either aspirin, dipyridamole, or trapidil was administered orally to patients with angina, A. M. I., and cerebral infarct for 4 weeks. The following results were obtained:
1) The proportions of constituent fatty acids in phospholipids (PE and PC) and of NEFA in plasma and platelets were not significantly influenced by any drug. This was particularly demonstrated by the very small change in the C
20:4 ratio.
2) The ADP-induced agglutination of platelets was significantly reduced in the aspirin and trapidil groups, particularly in the aspirin group.
3) The TX B
2 to 6-keto-PGF
1α ratio was significantly decreased in the aspirin and trapidil groups. These changes were explained by a significant reduction of TX B
2 in the trapidil group and by the marked reduction of TX B
2 in conjunction with an elevation of 6-keto-PGF
1α in the aspirin group. The reduced ratio in the dipyridamole group was similar to that in the trapidil group in mechanism.
4) These results suggest that trapidil and aspirin can be clinically effective in the prevention and treatment of thrombosis and in improving blood circulation in cases of arteriosclerosis.
View full abstract