Effect of Vitamin E on Platelet Aggregation in Diabetes Mellitus

SummaryVitamin E is known to be an inhibitor of platelet prostaglandin production and aggregation. The rate of platelet aggregation induced by adenosine diphosphate was significantly increased in diabetics with proliferative retinopathy and the enhanced production of thromboxane B2, a stable metabolite of thromboxane A2, was demonstrated in those patients. On the other hand, vitamin E in platelets was significantly reduced in diabetics compared with age matched controls. In addition, it was shown that vitamin E content in platelets examined in diabetic and control subjects inversely correlated with both the rate of platelet aggregation and thromboxane B2 production during aggregation. It is suggested that the reduced vitamin E levels in diabetic platelets can contribute to the mechanisms of the enhanced platelet thromboxane production and aggregation which relate to the development of vascular complications.

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Lack Of Inhibition Of Thromboxane Production Despite Inhibition Of Platelet Function By 1,3-Bis(2 Chloroethyl)-1-Nitrosourea (BCNU)

10.1055/s-0038-1652605 ◽

1981 ◽

Author(s):

R McKenna ◽

T Ahmad ◽

A Prancan ◽

D Simon ◽

H Frischer

Keyword(s):

Arachidonic Acid ◽

Oxygen Consumption ◽

Platelet Aggregation ◽

Acetylsalicylic Acid ◽

Platelet Function ◽

Human Platelet ◽

Thromboxane A2 ◽

Rabbit Aorta ◽

Thromboxane Production ◽

Platelet Thromboxane

We have previously shown that BCNU inhibits human platelet glutathione reductase (GSSG-R) prior to inhibiting platelet function; since thromboxane production is important in platelet function, we evaluated the effect of BCNU induced inhibition of GSSG-R on platelet thromboxane production.Control platelet GSSG-R activity was 0.091 ]jmoles NAD(P)H oxidized min-1lmg-1 protein at 37°C (±0.015 S.D.; n=9); inhibition was detectable at 10-7M% BCNU (70% of control) with a >90% inhibition at and above 10-5M BCNU. Platelet aggregation in response to 1.5×10-3M Arachidonic acid (AA), 10 μM epinephrine, 6 μg/ml equine collagen and 3 μM ADP were inhibited at 10-5M BCNU and abolished at 10-4 BCNU.BCNU (10-3M) did not affect the increase in oxygen consumption induced by AA. Using the rabbit aorta superfusion bioassay for thromboxane A2 (TXA2), threshold concentrations of AA in 10-5 and 10-4 BCNU platelets resulted in an increased measure of aortic tension 13.5 ± 9.4 mm S.D. (n=6) and 23.2 ± 9.5 mm respectively, compared with control values of 4.5 ± 2.4. Acetylsalicylic acid (5 × l0-4M) inhibited the contraction: 1.7 ± 1.1 (n=5). The conversion of 14C AA to thromboxane B2 (TXB2) and PGE2, as measured by radio TLC, was not decreased in BCNU treated platelets. There is a significant increase in TXB2 (p<0.05;n=4) and in the ratio of TXB2:PGE2 in platelets treated with 10-4M BCNU and 10-3M imidazole when compared to platelets treated with imidazole alone.In conclusion BCNU induced inhibition of platelet GSSG-R and platelet function occurs despite preservation of thromboxane production

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Effect of Indomethacin and Dazoxiben on Intravascular Platelet Aggregation in the Anaesthetized Rabbit

Thrombosis and Haemostasis ◽

10.1055/s-0038-1661607 ◽

1986 ◽

Vol 56 (01) ◽

pp. 080-085 ◽

Cited By ~ 6

Author(s):

A C Honey ◽

N Lad ◽

D P Tuffin

Keyword(s):

Platelet Aggregation ◽

Plasma Levels ◽

Thromboxane A2 ◽

Adenosine Diphosphate ◽

Thromboxane B2 ◽

Bolus Intravenous Injection ◽

Cyclic Endoperoxide ◽

High Doses ◽

Synthetic Capacity ◽

Dose Dependent

Summary Collagen (10-40 μg kg−1), thrombin (1-10 units kg−1), adenosine diphosphate (ADP; 3-300 pμ kg−1), 1-0-hexadecyl Paf-acether and 1-0-octadecyl Paf-acether (1-300 ng kg−1) administered by bolus intravenous injection each caused dose-dependent thrombocytopoenia accompanied by marked hypotension in anaesthetized rabbits. Responses to ADP and the Paf-acether derivatives were transient in nature (3-8 min) whereas those induced by collagen and thrombin were always of longer duration (5-20 min) and frequently fatal at high doses. Responses to collagen, thrombin, and the Paf-acether derivatives were invariably accompanied by substantial, dose-related increases in plasma levels of thromboxane B2 in samples obtained 30 s after agonist administration, whereas following ADP, no change in plasma thromboxane B2 was detected at any dose level. Indomethacin (3.0 mg kg−1 by infusion) had no effect on responses to thrombin or Paf-acether, partially inhibited collagen-induced thrombocytopenia, and potentiated responses to ADP. In contrast, dazoxiben (10 mg kg−1 by infusion) partially but significantly inhibited responses to thrombin, whereas those induced by collagen, Paf-acether or ADP were unchanged. These results indicate that in this model of intravascular aggregation, whilst platelet responses to collagen and thrombin appear partially dependent on intact cyclic endoperoxide and thromboxane A2 synthetic capacity respectively, responses to ADP and Paf-acether are independent of arachidonate metabolism via cyclo-oxygenase despite measurably increased TXB2 formation in the latter case.

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Platelet Aggregation in Whole Blood: The Role of Thromboxane A2 and Adenosine Diphosphate

Thrombosis and Haemostasis ◽

10.1055/s-0038-1660081 ◽

1985 ◽

Vol 54 (03) ◽

pp. 612-616 ◽

Cited By ~ 17

Author(s):

A J Carter ◽

S Heptinstall

Keyword(s):

Platelet Aggregation ◽

Whole Blood ◽

Adenosine Diphosphate ◽

Blood Platelet ◽

Thromboxane B2 ◽

Lipoxygenase Inhibitor ◽

Thromboxane Synthase Inhibitor ◽

Synthase Inhibitor

SummaryThe platelet aggregation that occurred in whole blood in response to several aggregating agents (collagen, arachidonic acid, adenosine diphosphate, adrenaline and thrombin) was measured using an Ultra-Flo 100 Whole Blood Platelet Counter. The amounts of thromboxane B2 produced were measured by radioimmunoassay. The effects of various inhibitors of thromboxane synthesis and the effects of apyrase, an enzyme that destroys adenosine diphosphate, were determined.Platelet aggregation was always accompanied by the production of thromboxane B2, and the amounts produced depended on the nature and concentration of the aggregating agent used. The various inhibitors of thromboxane synthesis - aspirin and flurbiprofen (cyclo-oxygenase inhibitors), BW755C (a cyclo-oxygenase and lipoxygenase inhibitor) and dazoxiben (a selective thromboxane synthase inhibitor) - did not markedly inhibit aggregation. Results obtained using apyrase showed that adenosine diphosphate contributed to the aggregation process, and that its role must be acknowledged when devising means of inhibiting platelet aggregation in vivo.

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THROMBOXANE-A2 MEDIATES THE ACTION OF INOSITOL (1.4.5) TRISPHOSPHATE (IP3) IN SAPONIN-PERMEABILISED PLATELETS

10.1055/s-0038-1644519 ◽

1987 ◽

Author(s):

K S Authi ◽

B J Evenden ◽

E J Hornby ◽

N Crawford

Keyword(s):

Phospholipase A2 ◽

Shape Change ◽

Thromboxane A2 ◽

Thromboxane B2 ◽

Cyclooxygenase Inhibitors ◽

Storage Site ◽

Platelet Surface ◽

Surface Receptors ◽

Thromboxane Receptor ◽

Thromboxane Production

Inositol trisphosphate (IP3) has now been identified as an important intracellular second messenger that can initiate the release of Ca2+ from intracellular stores in a variety of cells, including platelets. We have studied the effects of IP3 on washed platelets permeabilised with saponin (12-14 μg/mi) which allows penetration into the cell of low M.Wt polar molecules. The permeabilised cells show normal responses to the agonists thrombin and collagen. The addition of IP (1-20 μM) after saponin treatment induces shape change, aggregation and secretion of preloaded [14C] 5HT. Concomitant with these responses, thromboxane is produced in a dose related manner. With 20 μM IP3 thromboxane B2 increases from basal levels of 5-4 ± 3-0 ng/ml to 140 ± 23 ng/ml. Both thromboxane production and the platelet responses induced by IP3 are inhibited by pretreatment with the cyclooxygenase inhibitors, indomethacin (EC50 50 μM) and aspirin (EC50 30 μM). Aggregation and secretion responses to IP3 are also inhibited by thromboxane B2 receptor agonists; EPO 92 (R. Jones, Edinburgh) and AH 23848 (Glaxo Ltd.). If Ca2+ EGTA buffers age used with permeabilised platelets to "lock" the cytosolic [Ca2+] at 0.1 μM, thromboxane production is reduced to the basal level. Intact platelets were labelled with Ca2+ (4h incubation) and after washing, resuspension and saponisation, IP3 induced the release of 20% of the cell associated Ca2+. The release was unaffected by pretreatment with antimycin and oligomycin indicating an gndoplasmic reticulum-lige storage site for the sequestered Ca2+. This IP3 -induced Ca2+ release was also not affected by pretreatment with either cyclooxygenase inhibitors or thromboxane receptor antagonists (EPO 92 and AH 23848). We believe these studies indicate that the action of IP3 in sagonised platelets involves release of intracellularly stored Ca2+, activation of phospholipase A2 and cyclooxygenase, and production of thromboxane A2. The release of thromboxane mediates and/or attenuates platelet responses by acting upon platelet surface receptors.

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Lipid peroxidation, prostacyclin and thromboxane A2 in pigs depleted of vitamin E and selenium and supplemented with linseed oil

British Journal Of Nutrition ◽

10.1079/bjn19950141 ◽

1995 ◽

Vol 74 (3) ◽

pp. 369-380 ◽

Cited By ~ 8

Author(s):

Maeve R. Nolan ◽

Seamus Kennedy ◽

W. John Blanchflower ◽

D. Glenn Kennedy

Keyword(s):

Lipid Peroxidation ◽

Arachidonic Acid ◽

Vitamin E ◽

Platelet Aggregation ◽

Plasma Concentration ◽

Linseed Oil ◽

Thromboxane A2 ◽

Dietary Factors ◽

Biochemical Effects ◽

Skeletal Myopathy

In a 2×2 balanced factorial experiment the biochemical effects on pigs of two dietary factors were investigated. The first factor was α-tocopherol and Se supplementation and the second factor was supplementation with α-tocopherol-stripped linseed oil. In pigs fed on diets depleted of α-tocopherol and Se, increases in concentrations of markers of lipid peroxidation (4-hydroxynonenal and hexanal) were observed. However, skeletal myopathy was only observed in those pigs fed on diets depleted of α-tocopherol and Se and supplemented with oil. In those pigs, increased lipid peroxidation was observed in heart and supraspinatus muscle. The plasma concentration of thromboxane B2 was increased in pigs fed on diets depleted of α-tocopherol and Se, suggesting an increased tendency towards platelet aggregation. However, this change was reversed in pigs depleted of α-tocopherol and Se, but supplemented with oil. This may have been a consequence of loss of arachidonic acid, the substrate for thromboxane formation, as a result of lipid peroxidation.

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Fibrinogen-independent aggregation and deaggregation of human platelets: studies in two afibrinogenemic patients

Blood ◽

10.1182/blood.v70.1.221.221 ◽

1987 ◽

Vol 70 (1) ◽

pp. 221-226 ◽

Cited By ~ 25

Author(s):

M Cattaneo ◽

RL Kinlough-Rathbone ◽

A Lecchi ◽

C Bevilacqua ◽

MA Packham ◽

...

Keyword(s):

Platelet Aggregation ◽

Plasma Proteins ◽

Platelet Rich Plasma ◽

Platelet Activating Factor ◽

Adenosine Diphosphate ◽

Human Platelets ◽

Human Fibrinogen ◽

Control Subjects ◽

Platelet Aggregates ◽

And Control

Abstract Platelets from two afibrinogenemic patients were used to determine whether fibrinogen is essential for platelet aggregation and to examine whether released fibrinogen contributes to the stabilization of platelet aggregates when platelets have been induced to aggregate and release their granule contents by stimulation with thrombin. The addition of adenosine diphosphate (ADP) to platelet-rich plasma (PRP) or to suspensions of washed platelets from the afibrinogenemic patients caused the formation of small aggregates, which was either not inhibited or only slightly inhibited by the F(ab')2 fragments of an antibody to fibrinogen but was inhibited by an antibody (10E5) to glycoprotein IIb/IIIa. Thus there is a component of ADP-induced platelet aggregation that is not dependent on fibrinogen or other plasma proteins but is dependent on glycoprotein IIb/IIIa. There was little difference in the extent of aggregation and the release of granule contents of normal and afibrinogenemic platelets in response to the release-inducing agents collagen, platelet-activating factor (PAF), sodium arachidonate, or thrombin. With normal or afibrinogenemic platelets, aggregation by thrombin (0.2 U/mL or higher) was not inhibited by the F(ab')2 fragments of an antibody to human fibrinogen. Deaggregation by combinations of inhibitors of platelets aggregated by 1 U/mL thrombin showed no difference between platelets from afibrinogenemic and control subjects, indicating that released fibrinogen does not make a major contribution to the stabilization of platelet aggregates formed by thrombin stimulation.

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A Study of Intravascular Platelet Aggregation in the Rat

10.1055/s-0039-1687231 ◽

1979 ◽

Author(s):

G. G. Duncan ◽

G. M. Smith

Keyword(s):

Arachidonic Acid ◽

Platelet Count ◽

Platelet Aggregation ◽

Thromboxane A2 ◽

Adenosine Diphosphate ◽

Residual Response ◽

Induced Aggregation ◽

Anaesthetized Rat

Intravascular platelet aggregation can be studied by measuring the fall in the circulating platelet count induced by aggregating agents in anaesthetized animals. The Technicon Auto-counter was modified and connected via a double cannula to an anaesthetized rat to give a continuous count of the number of circulating platelets (1). Adenosine diphosphate (ADP), Collagen, Arachidonic acid (AA) and 5-Hydroxytryptamine (5-HT) were given at 15 minute intervals over a period of 2-3 hours. Aspirin (10 mg/Kg IV ) and Indomethacin (1-8 mg/Kg IV) partially inhibited collagen-induced aggregation and Indomethacin (2 mg/Kg IV) completely inhibited AA-induced aggregation. Adenosine (0.25 mg/min) inhibited the ADP-induced aggregation but did not inhibit aggregation produced by collagen or the residual response to collagen that remains after the addition of indomethacin.Reproducible responses to ADP and collagen were obtained but responses to AA and 5-HT were not reliable. Collagen-induced aggregation is thought to be mediated by the liberation of ADP, 5-HT and the formation of prostaglandin (PG ) endoperoxides and thromboxane A2. This study has shown that collagen-induced aggregation is reduced by inhibition of PG synthesis but the involvement of ADP or 5-HT could not be shown.

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Thrombocyte hemostasis disorders in patients with arterial hypertension at different terms after survived hemorrhagic stroke

Kazan medical journal ◽

10.17750/kmj2015-722 ◽

2015 ◽

Vol 96 (5) ◽

pp. 722-727 ◽

Cited By ~ 1

Author(s):

G Kh Mirsaeva ◽

R A Khakimova ◽

I R Timershina

Keyword(s):

Platelet Count ◽

Platelet Aggregation ◽

Arterial Hypertension ◽

Software Package ◽

Hemorrhagic Stroke ◽

Standard Treatment ◽

Statistical Data ◽

Vascular Complications ◽

Adenosine Diphosphate ◽

Rehabilitation Period

Aim. To analyze the indices of platelet link of hemostasis in patients with arterial hypertension at different periods after surviving hemorrhagic stroke. Methods. 82 patients with arterial hypertension stage 3 were followed up after surviving the hemorrhagic stroke. The following indicators of platelet hemostasis were studied: platelet count, spontaneous aggregation of thrombocytes; adenosine diphosphate aggregation of thrombocytes induced by adenosine diphosphate, collagen and ristomycin. The laboratory test were performed at admission before the standard treatment was initiated, and at discharge. Statistical data were processed using the integrated Statistica 8.0 software package for Windows (StatSoft). Results. All examined patients had signs of thrombocyte hemostasis activation. In patients with arterial hypertension, reduced platelet count and increased functional activity of thrombocytes was revealed in early rehabilitation period after hemorrhagic stroke, characterized by non-significant increase of spontaneous and induced platelet aggregation. In patients with arterial hypertension in late rehabilitative period and in residual period after surviving the hemorrhagic stroke, a study of primary stage of platelet hemostasis showed statistically significant deviations of platelet aggregation, seen as the increased spontaneous and induced platelet aggregation, indicating chronic hypercoagulation. Conclusion. Presented data of platelet link of hemostasis alterations may indicate a higher risk of thrombosis in patients with arterial hypertension over time after surviving the hemorrhagic stroke which may lead to recurring vascular complications.

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Prostaglandin Endoperoxides and Thromboxanes: Role in Platelets

10.1055/s-0039-1682631 ◽

1977 ◽

Author(s):

Bengt Samuelsson

Keyword(s):

Smooth Muscle ◽

Platelet Aggregation ◽

Vascular Smooth Muscle ◽

Thromboxane A2 ◽

Human Platelets ◽

Thromboxane B2 ◽

Structural Work

Two groups of unstable (t1/2=5 min) endoperoxides, PGG and PGH compounds, have been isolated and shown to be precursors of the prostaglandins. The endoperoxides cause platelet aggregation and contract vascular and air-way smooth muscle.A new group of compounds(thromboxanes) derived from the endoperoxides has been discovered. A highly unstable(t1/2=30-40 sec) intermediate, thromboxane A2, between the endoperoxides and thromboxane B2 has been detected. Structural work indicates that it has a bicyclic oxane-oxetane structure. Thromboxane A2 is a potent aggregating agent with pronounced effects on vascular smooth muscle. Studies on the mechanisms of actions of the endoperoxides and thromboxanes in human platelets will be discussed.

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