Effects of verapamil on platelet aggregation and serum thromboxane synthesis in vitro and in vivo

The aim of this study was to evaluate the in vitro effects of verapamil on platelet aggregation and serum thromboxane formation. We also studied the in vivo effects of verapamil retard on platelet aggregation and serum thromboxane formation. The incubation of verapamil with PRP produced a dose-dependent decrease of in vitro platelet aggregation for all the agents used. Potentiation by verapamil of antiaggregating activity of prostacyclin was also demonstrated; in fact when verapamil and prostacyclin were added simultaneously a synergistic inhibition of platelet aggregation by ADP was observed. In whole blood verapamil partially inhibited thromboxane production only at a higher concentration. In vivo verapamil significantly decreased platelet aggregation induced by ADP and epinephrine while no changes were observed after arachidonic acid. No significant changes occurred in serum TXB2 levels. The observations suggest a potential role for verapamil in antithrombotic therapy as an antiplatelet agent.     

Effects of tomato extract on human platelet aggregation in vitro

Among all fruits tested in vitro for their anti-platelet property, tomato had the highest activity followed by grapefruit, melon, and strawberry, whereas pear and apple had little or no activity. Tomato extract (20-50 w l of 100% juice) inhibited both ADP- and collagen-induced aggregation by up to 70% but could not inhibit arachidonic acid-induced platelet aggregation and concomitant thromboxane synthesis under similar experimental conditions. The anti-platelet components (MW <1000 Da) in tomatoes are water soluble, heat stable and are concentrated in the yellow fluid around the seeds. The active fractions were separated using gel filtration and HPLC. The aqueous fraction (110 000 2 g supernatant) of tomatoes containing anti-platelet activity was subjected to gel filtration column chromatography (Biogel P2 column). The activity was fractionated into two peaks, peak-3 and peak-4 (major peak). Subsequently, peak-4 was further purified by HPLC using a reversed-phase column. NMR and mass spectroscopy studies indicated that peak F2 (obtained from peak 4) contained adenosine and cytidine. Deamination of peak F2 with adenosine deaminase almost completely abolished its anti-platelet activity, confirming the presence of adenosine in this fraction. In comparison, deamination of peak-4 resulted in only partial loss of inhibitory activity while the activity of peak-3 remained unaffected. These results indicate that tomatoes contain anti-platelet compounds in addition to adenosine. Unlike aspirin, the tomato-derived compounds inhibit thrombin-induced platelet aggregation. All these data indicate that tomato contains very potent anti-platelet components, and consuming tomatoes might be beneficial both as a preventive and therapeutic regime for cardiovascular disease.     

Effects of moderate alcohol consumption on platelet aggregation, fibrinolysis, and blood lipids

To investigate the effect of moderate alcohol consumption on blood constituents related to cardiovascular disease, 12 male volunteers consumed (instead of their usual alcoholic drinks) four different standardized amounts of red wine in addition to their habitual diet. Each dose was given to the subjects during a period of 5 weeks in a randomized order, all subjects receiving the four doses. They consisted of 0, 2, and 4 glasses/d, providing 0, 23, and 46 g alcohol/d as well as in "binge drinking" (14 glasses in the weekend, comparable to an average of 2 glasses/d). The results showed a clear dose-related response to the drinking for several blood constituents. Most marked was a decrease in the tissue-type plasminogen activator activity and to a lesser degree an increase in plasminogen levels. Collagen-induced platelet aggregation was reduced, affecting all parameters measured. Levels of HDL3-cholesterol, gammaglutamyltransferase, and urate showed a small but significant increase. No change was noted in the levels of alkaline phosphatase, alanine-aminotransferase, aspartate-aminotransferase, bile acids, folate, fibrinogen, the ADP-induced platelet aggregation, platelet secretion, or in hematologic values. The results are only partially in accordance with the presumed protective action of moderate drinking on the cardiovascular system and show a stronger response to the consumption of alcohol in coagulation and fibrinolysis factors than in blood lipids.     

Influence of acute alcohol exposure on hemorheological parameters and platelet function in vivo and in vitro

We have analysed the influence of acute alcohol exposure in vivo and in vitro on blood flow properties and platelet function. 12 healthy male volunteers drank either 4.36 ml red wine/kg body weight (=0.5 g ethanol/kg) or water at 06.00 p.m. under fasting conditions. Blood was drawn immediately before, and 1, 2, 4 and 13 h after alcohol ingestion. Alcohol had a detectable osmotic effect on erythrocytes; the mean cellular volume (MCV) was significantly smaller 1-4 h after ingestion. Whole blood viscosity remained unaffected, but blood viscosity at a standardized Hct of 45% measured at a high shear rate (94.5 s(-1)) was increased 2 h after wine ingestion. In the morning, 13 h after wine drinking, platelet aggregation measured with a platelet function analyser PFA-100 was increased to a greater extent than after water drinking. In vitro, no effect was seen when blood was incubated with 0, 12.5, 25, 50 and 100 mmol/l ethanol for 1 h at 37 degrees C. We conclude that an acute exposure to alcohol has only modest effects on hemorheological parameters and platelet aggregation in vivo and no effect in vitro, which suggests that other factors must be involved in both beneficial and harmful effects of wine drinking.     

Effects of polyamines on platelet aggregation

Polyamines, spermine and spermidine in the micromolar range (1-100 mumol/l) increase ADP and epinephrine-induced platelet aggregation in vitro. The possible r?le of polyamines as regulating factors of platelet aggregation in physiological and pathological states is discussed.     

The in vitro and in vivo evaluation of tilorone hydrochloride as a platelet aggregation inhibitor.

Tilorone hydrochloride was tested in vitro for inhibition of platelet aggregation in the ADP, collagen, and epinephrine-induced platelet aggregation systems. Tilorone did not significantly inhibit the first phase of platelet aggregation induced by ADP, but was a very potent inhibitor of the second phase of platelet aggregation (release reaction) as illustrated by the epinephrine-induced system. When the compound was given to rats by stomach tube at 100 mg/kg for 2 doses, 24 h apart and blood taken 24 h after the second dose, an inhibition of collagen-induced platelet aggregation was found. This result is interpreted as inhibiting the release reaction and second phase platelet aggregation.     

The in vitro effects of verbascoside on human platelet aggregation

Preliminary in vitro and animal studies have shown that verbascoside, a phenolic compound, may have several favourable biological activities, including an influence on endothelial function and on platelet aggregation. We sought to evaluate the effects of verbascoside, biotechnologically produced from plant cell cultures, on human platelet aggregation (PA). The blood from 40 aspirin-na?ve volunteers with at least one cardiovascular risk factor was preincubated in vitro with verbascoside (1 and 2?mg/dL) and aspirin (100?μM). The blood from 20 patients with a prior diagnosis of coronary heart disease who were chronically assuming aspirin was preincubated in vitro with verbascoside (1 and 2?mg/dL). PA is measured with a light transmission aggregometry and multiplate analyzer. As compared to reference, preincubation with verbascoside resulted in a significant inhibition of adenosine diphosphate (ADP) and arachidonic acid (AA)-induced PA (p?相似文献   

Effects of desmopressin on platelet membrane glycoproteins and platelet aggregation in volunteers on clopidogrel

PURPOSE: The use of clopidogrel is standard in interventional cardiology. Haemorrhage occurs in some patients, which implies a need for a non-transfusional therapy. Desmopressin showed its efficacy as an antidote of acetylsalicylic acid. In this trial the effects of desmopressin on platelet glycoproteins and the platelet's ability to aggregate under the influence of clopidogrel are studied. METHODS: The trial was conducted as an open, prospective, single-centre, randomised pilot study with n=17 healthy volunteers in a parallel-group design. 1 h after an oral loading dose of 375 mg clopidogrel the effects of a single-dose of 300 mug of Octostim nasal spray (n=9) on platelet aggregation, activity of platelets on the density of membrane-bound receptors are measured. RESULTS: Ristocetin cofactor and platelet reactivity rose significantly after the administration of Octostim nasal spray with 31.9% and 5.3%, respectively (p=0.0329; p=0.0414). The ADP-induced platelet aggregation increased after the administration of Octostim nasal spray by approximately 20% (p=0.0564). The fraction of CD62- and CD63-positive platelets did not change after clopidogrel nor after desmopressin (p=0.4203; p=0.6774). The density of GPIIb/IIIa receptors per platelet did not change after desmopressin (p=0.9652). The density of GPIb/IX receptors per platelet rose after desmopressin without reaching the level of significance (p=0.0802). In the desmopressin group alone the receptor density rose by 5.5% (p=0.0783). CONCLUSION: The administration of desmopressin improved the primary haemostasis when given in addition to a clopidogrel therapy. Patients undergoing a heart catheter procedure with clopidogrel might benefit from the use of desmopressin when having a bleeding episode.