Effects of Green Tea Catechin on Phospholipase A₂ Activity and Antithrombus in Streptozotocin Diabetic Rats

Abstract

The purpose of this study was to investigate the effects of dietary green tea catechin on phospholipase A₂ (PLA₂) activity and the antithrombotic reaction of platelets in streptozotocin (STZ)-diabetic rats. Sprague-Dawley male rats weighing 100±10g were randomly divided into one normal and three STZ-diabetic groups, which were subdivided into catechin-free group (DM-OC), 0.5% catechin group (DM-0.5C) and 1% catechin group (DM-1C). The activity level of platelet phospholipase A₂ was higher in the diabetic groups than in the normal group, while it was lower in DM-0.5C and DM-1C than in DM-OC. The activity of platelet cyclooxygenase in DM-OC was 1.1-fold as high as in the normal group, but was significantly reduced by catechin supplementation. The platelet thromboxane A₂ (TXA₂) formation became higher in DM-OC as compared to the normal group, but not in DM-0.5C and DM-1C. The synthesis of aortic prostacyclin (PGI₂) was lower in DM-OC and DM-0.5C than in the normal group. The PGI₂/TXA₂ ratio was decreased to 55% in DM-OC, but was restored by catechin supplementation. These results indicate that STZ-diabetic rats are sensitive to platelet aggregation and thrombosis, and that the abnormality can be improved by dietary catechin.