| Cylic nucleotides (including cAMP and cGMP) and calcium ion (Ca2+) are two important signallings which regulate each other. Phosphodiesterase (PDE) regulates the levels of cylic nucleotides and then Ca2+. Some study show that, several PDE subtypes of certain tissues either accelerated or postponed the onset and development of certain diseases. Platelet plays a key role on the onset and development of thrombosis diseases and platelet comprises serveral phosphodiesterase subtype, so we guess that the activity of platelet PDE and levels of Ca2+ of patients suffering cerebral thrombosis may differ from those of the healthy. Ginkgo biloba extract (EGB) is the most widely used herbal drug in China and the west countries presently. It comprises multitude components and has numerous pharmacal activities. Clinical pharmacal investigation indicates that certain drugs such as cilostazol and MY5445 could supress platelet functions through inhibiting the activity of platelet phosphodiesterase then increasing levels of cAMP, decreasing concentration of free calcium ion (Ca2+i). Recently some authors report that EGB could regulate some PDE subtype of certain tissues. EGB have definite antiplatelet aggregative activity, whether is it also through effecting the activity of platelet PDE to inhibit platelet aggregation? Objective: 1. To observe the variation of platelet PDE activity, cylic nucleotides levels and free calcium ion concentration of patients with acute cerebral infarction. 2. To investigate the effect of EGB on platelet aggregation, PDE activity, nucleotide cyclase activities, cyclic nucleotide levels and Ca2+i concentrations in vitro, and investigate the mechanisms of EGB anti-platelet aggregation. Observe the different effect of EGB alone and EGB combined with dipyridamole on human platelet functions and investigate mechanisms of their synergistic action. 3. To observe the effect of EGB on PDE3 activity, cAMP levels and Ca2+i concentrations in patients with acute cerebral infarction. Verify the therapeutic effect of EGB on acute cerebral infarction. Methods: 1. PDE3 activity, cAMP levels and Ca2+i concentrations of 30 acute cerebral infarction patients were detected on 1st, 4th, 8th, and 15th day after onset. Ten healthy individuals of the same age range were chosen as control group. 2. Blood samples from 3 healthy volumteers who have not taken any drugs two weeks before experiments were anticoagulated with 3.8% sodium citrate. After isolating and washing, platelet was treated with various concentration of EGB, dipyridamole, EGB combined with dipyridamole respectively, and then were applied for the measure of platelet aggregation (use turbidimetric method), cyclic nucleotides levels (use EIA method) and Ca2+i concentration (determined by CLSM after platelet were loaded with Fluo-3AM). The activities of PDE subtypes, AC and GC isolated from platelet sonic homogenates were determined by EIA. Control groups were treated with the same bulk drug solvent. The activity of PDE express as pmol cAMP or cGMP hydrolyzed/mg protein/min, and AC, GC as pmol cAMP or cGMP formed/mg protein/min. 3. Fifteen patients with acute cerebral infarction received EGB in addtion to common therapy. Control group (the 30 patients mentioned above) received only common therapy. Platelet PDE3 activity, cAMP levels and Ca2+i concentration of both groups were detected in various time (pretreatment and 1st, 3rd, 7th, 14th day post-treatment). Clinic indexes (neurologic impairment and hemorrheology) were evaluated on pretreatment and 14th day post-treatment. Results: 1. Within two weeks cerebral infarction onset, Platelet PDE2, PDE3 activity and cAMP levels decreased, Ca2+i levels increased, PDE5 activity and cGMP levels have not changed. Ca2+i is linear correlated with cAMP. However, there is no correlation among PDE2, PDE3, Ca2+i and cAMP. 2. EGB dose-dependently inhibited platelet aggregation induced by ADP or PAF, increased platelet cAMP, inhibited PDE3 activity and inhibited the increase of Ca2+i induced by ADP or PAF. EGB at high dose s...
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