[Change in the structure and number of blood platelets during intravenous activation of the blood coagulation system].
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Animals↗
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Results for “Blood Platelets”
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Sex differences in ABO blood types distribution in manic-depressive patients and in the rate of 5-HT uptake by blood platelets in healthy donors of different blood groups.
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ABO Blood-Group System↗
Reduced blood platelet sensitivity to aspirin in coronary artery disease: are dyslipidaemia and inflammatory states possible factors predisposing to sub-optimal platelet response to aspirin?
The study was designed to assess blood platelet sensitivity to acetylsalicylic acid and its associations with dyslipidaemia and inflammation in coronary artery disease patients. Platelet non-responsiveness to aspirin is associated with an increased risk of serious cardiovascular events. Several environmental and hereditary factors are reportedly involved in sub-optimal acetylsalicylic acid response. Forty-five coronary artery disease patients and 45 non-coronary artery disease controls received acetylsalicylic acid at a daily dose of 75-150 mg. Controls were examined twice: on the day of entering the study and 10 days later. Urinary 11-dehydrothromboxane B2 was assessed as the marker of platelet thromboxane generation. Aggregation was studied in platelet-rich plasma using turbidimetric aggregometry with collagen and arachidonic acid. Fifty to seventy percent of coronary artery disease patients showed an extent of collagen-induced aggregation above the upper quartile of the reference range compared with 8-15% in controls (P<0.003). For arachidonic acid-activated aggregation these proportions were 45-50% in coronary artery disease versus 7% in controls (P<0.007). In coronary artery disease patients, the acetylsalicylic acid-mediated platelet inhibition positively correlated with increased triglycerides (in arachidonic acid-stimulated platelets, r=0.30, P=0.0018), total cholesterol (r=0.33, P<0.0001 in coll and arachidonic acid-activated platelets) and elevated serum C-reactive protein (CRP) (r=0.27, P=0.0024). In coronary artery disease patients urine 11-dehydrothromboxane B2 concentrations were significantly increased compared to controls after 10 day acetylsalicylic acid intake (563; 313-728 pg/mg creatinine versus 321; 246-488 pg/mg creatinine, P=0.04). The incidence of suboptimal acetylsalicylic acid response incidence was more common in patients with coronary artery disease. Acetylsalicylic acid inhibition of blood platelet reactivity and thromboxane generation was less effective in these patients. Dyslipidaemia and chronic inflammatory states may promote suboptimal acetylsalicylic acid response in coronary artery disease patients.
Anti-Inflammatory Agents, Non-Steroidal↗
Increased protein glycation in diabetes mellitus is associated with decreased aspirin-mediated protein acetylation and reduced sensitivity of blood platelets to aspirin.
Reduced effectiveness of the most common antiplatelet drug, acetylsalicylic acid (ASA, aspirin), in diabetes mellitus has been associated with a lowered platelet sensitivity to ASA and related to glycemic control in diabetic patients. Our objectives were (a) to monitor the chemical background of how chronic hyperglycemia affects platelet response to ASA in diabetes and (b) to study a chemical competition between the amount of bound acetyl residues and the extent of protein glycation in blood platelets. Using whole-blood impedance aggregometry and platelet function analyzer (PFA-100) we observed a reduced platelet response to ASA in diabetic patients (14% vs. 79% for PFA-100 collagen-epinephrine occlusion time) and an association between the index of glycemic control and platelet refractoriness to ASA (r(S) = -0.378). Impaired platelet response to ASA was related to enhanced platelet protein glycation (3.6+/-0.4 in diabetes vs. 2.3+/-0.4 micromol fructosamine/microg protein in control) and reduced incorporation of acetyl residue into proteins of platelets from diabetic patients (47.4+/-2.0 in control vs. 33.1+/-0.7 micromol acetyl/microg protein in diabetic subjects). Incubation of blood platelets with increasing concentrations of glucose and ASA under in vitro conditions led to excessive modification in protein amino groups: glucose and ASA competed with each other in the course of nonenzymatic modifications, glycosylation, or acetylation, and their contributions to the occupancy of protein amino groups (R2 = 0.22 for glucose, R2 = 0.43 for ASA) were dependent upon the concentrations of glucose and ASA. Overall the effects of high glucose and high ASA on the overall occupancy of protein free amino groups are not additive. While at higher concentrations ASA overcomes the effects of hyperglycemia and retards glycation, high glucose makes acetylation less efficient, and therefore the resultant chemical modification becomes greatly reduced. In conclusion, diminished susceptibility of various platelet proteins and receptors on blood platelet membranes to acetylation and high ambient glucose might underlie the apparently differentiated sensitivity of blood platelets to ASA and determine platelet "insensitivity to aspirin" in diabetic patients.
Acetylation↗
Evidence for the existence of high affinity binding sites for indomethacin on human blood platelets.
Using human blood-washed platelets and [3H]indomethacin, we demonstrated the presence of saturable, time- and temperature-dependent high affinity binding sites for non-steroidal anti-inflammatory drugs. The observed Kd value for indomethacin was 5 nM. Structural specificity of the non-steroidal anti-inflammatory drug site was studied with arylacetic acids, anthranilic acids, and compounds from other chemical families. Arylacetic acid drugs had affinities which were similar to the affinity of indomethacin. Affinity differences among the other drugs may be related to the presence or absence of the lipophilic substituent on the central ring. As expected, anti-inflammatory pyrrazole derivatives, aspirin, bucloxic acid, cortisol, nordihydroguaiaretic acid, and the chemotactic peptide formyl-Met-Leu-Phe were not recognized by the indomethacin binding site.
Anti-Inflammatory Agents↗
Generation of reactive oxygen species in blood platelets.
The generation of superoxide anion radicals (O2*-) and the other reactive oxygen species (ROS) was estimated by means of cytochrome c reduction and chemiluminescence, as well in resting blood platelets and in platelets stimulated by thrombin in the presence or absence of some inhibitors of pathways involved in platelet activation. We used allopurinol (xanthine oxidase inhibitor), wortmannin (PI 3-kinase inhibitor) and staurosporine (protein kinase C inhibitor). To determine the involvement of the glutathione in ROS generation, we used L-buthionine sulfoximine (BSO) which blocks GSH synthesis. Our results confirmed that thrombin stimulates the production of ROS concomitant with metabolism of arachidonate and production of malonyldialdehyde (MDA) in blood platelets (P < 0.05) and showed that, in the presence of inhibitors, the generation of ROS in platelets (resting and stimulated) was reduced. This indicates that xanthine oxidase, PI 3-kinase or protein kinase C take part in the formation of ROS in blood platelets. Moreover, adhesion of platelets to fibrinogen and secretion of adenine nucleotides from platelets after wortmannin and staurosporine action was also inhibited. BSO not only decreased GSH level, but also reduced the amount of ROS; a correlation between the depletion of GSH and the decrease of ROS was observed (R = -0.987; P < 0.02). It is concluded that in blood platelets, ROS are produced in the receptor-mediated signaling pathways and platelet activation (arachidonic acid metabolism, the glutathione cycle, metabolism of phosphoinositoides and due to xanthine oxidase). Our results support the importance of ROS in platelet function.
Animals↗
The microfilamental system of human blood platelets.
The major microfilamental protein of human blood platelets is actin. It has been estimated to constitute 20-50% of total platelet proteins. The organization of actin filaments within the cell is regulated by their association with other proteins. This review will focus on the composition, the cellular organization and on the functions of the microfilamental system in unstimulated and stimulated platelets.
Actin Cytoskeleton↗
The effect of iproniazid and imipramine on the blood platelet 5-hydroxytrptamine level in man.
Observations are reported on the blood platelet 5-hydroxytryptamine content of six patients receiving imipramine, N-(gamma-dimethylaminopropyl)-iminodibenzyl hydrochloride. The response was a fall to a level of one-sixth of the original in three weeks, with little change thereafter. This is in sharp contrast to the action of iproniazid which caused a rise of some 200% in the blood platelet 5-hydroxytryptamine level over the same period. Imipramine in a concentration of 1 mg./ml. had no inhibitory action on 5-hydroxytryptophan decarboxylase; 8.0 mug./ml. of imipramine suppressed two-thirds of the in vitro uptake of 5-hydroxytryptamine (2.5 mug./ml.) by normal human platelets.
Aromatic-L-Amino-Acid Decarboxylases↗
Selenium compounds inhibit the biological activity of blood platelets.
The action of inorganic forms of selenium (Se) on blood platelet aggregation, secretion and the arachidonate pathway in vitro was studied. It was shown that sodium selenite, after 30 min preincubation, inhibited platelet aggregation induced by 0.1 U/ml of thrombin and by 10 microM ADP (about 30% inhibition of aggregation after pretreatment of platelets with 10(-4) M of Se). Contrary to sodium selenite, sodium selenate did not affect the platelet aggregation induced by either agonist. Pretreatment of blood platelets with sodium selenite resulted in a statistically significant decrease in adenine nucleotide secretion ( P < 0.01) and release of malonyldialdehyde (MDA), produced in equal amounts to TXA(2) , in thrombin-stimulated platelets ( P <0.001). However, selenite did not change the level of MDA/TXA(2) in sodium arachidonate-stimulated platelets. We conclude that the inhibitory effects of sodium selenite on platelet activation could be the result of decreased synthesis and release of secondary agonists (TXA(2), ADP) in stimulated platelets. It is also possible that sodium selenite blocks the release of arachidonic acid from platelet membranes via phospholipases.
Journal Article↗
Immunocytochemical localization of albumin and factor XIII in thin cryo sections of human blood platelets.
Albumin and factor XIII alpha 2 were localized in human blood platelets by immunofluorescence and protein A-colloidal gold immuno-electron microscopy using thin and ultrathin cryosections of mildly fixed human blood platelets. Albumin was found in alpha-granules, co-distributing with beta-thromboglobulin in double label experiments. In platelets directly fixed in plasma, without previous washing, albumin was also localized on the plasma membrane and in the surface connecting system. Factor XIII alpha 2 was localized diffusely through the entire cytoplasmic matrix.
Blood Platelets↗
Prolonged bleeding time in Aleutian mink associated with a cyclo-oxygenase-independent aggregation defect and nucleotide deficit in blood platelets.
A prolonged mean template bleeding time of 13 minutes was present in nine Aleutian mink affected with Chediak-Higashi syndrome (CHS) compared with 4 minutes in dark control mink. The concentrations of blood platelets in normal and affected animals did not differ significantly. However, in mink with CHS, a marked disturbance of platelet response to collagen was present. Administration of aspirin and indomethacin completely blocked CH platelet response to collagen. Blood platelet adenosine triphosphate and adenosine diphosphate values from mink with CHS were significantly less than those of normal mink, and the platelet adenosine triphosphate/adenosine diphosphate ratios were 10.31 in affected mink and 2.74 in normal mink. These findings are consistent with our previous investigations in affectd cattle and persons and indicate that a "storage pool disease" of platelets exist in the mink with CHS.
Adenine Nucleotides↗
[Transfusion of blood platelets].
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Blood Platelets↗
The protective effects of resveratrol against changes in blood platelet thiols induced by platinum compounds.
Cisplatin (cis-diamminedichloroplatinum II, cisPt) is especially useful in the treatment of epithelial malignancies, however, the use of cisplatin is accompanied by several toxicities including haematological toxicity. Contrary to cisplatin, selenium-cisplatin conjugate ((NH(3))(2)Pt(SeO(3)); Se-Pt) has only a slight toxicity effect on blood platelet function. In the mechanism of platinum compounds action on platelets thiols are involved. The aim of the present studies was to examine in vitro how trans-resveratrol (trans-3,4',5-trihydroxystilbene) acts on the levels of platelet glutathione (GSH) and other thiol-containing compounds and how, as an antioxidant, protecs blood platelets against the oxidative stress caused by platinum compounds (cisPt and Se-Pt). To analyse the level of thiols in human blood platelets treated with platinum compounds and with resveratrol the classical technique HPLC has been used. Blood platelets isolated by differential centrifugation of human blood were incubated (30 min, 37 degrees C) with cisPt or Se-Pt at dose of 10 microg/ml that inhibits platelet function and with resveratrol (25 microg/ml). The obtained results indicate that platinum compounds caused in platelets a decrease of both, reduced glutathione (GSH) and free thiols of cysteine (CSH) and cysteinylglycine (CGSH). The pool of these compounds in unreduced form was increased. Platinum compounds caused the reduction of platelet protein thiols. Resveratrol (after 30 min action) at the concentration of 25 microg/ml partly reduced the platinum compounds induced decrease of platelet thiols, particularly thiols in acid-soluble fraction.
Antioxidants↗
gamma-Aminobutyrate aminotransferase activity in blood platelets of six species.
1. The kinetic parameters of gamma-aminobutyrate aminotransferase (GABA-T) were studied in washed blood platelets from cat, dog, horse, man, mouse and rat. 2. Wide differences were found in the maximal reaction velocity (Vmax) of GABA-T in blood platelets of the six species. 3. A significant increase in the activity of GABA-T was found in the blood platelets of adult rats as compared to those of young rats. 4. However, there was no significant difference in the activity of platelet GABA-T between male and female rats. 5. The activity of human platelet GABA-T estimated in platelet-rich plasma from healthy male subjects was found to be decreased in the presence of plasma and albumin. 6. The decrease was due to the specific binding of the cofactor pyridoxal phosphate to plasma albumin.
4-Aminobutyrate Transaminase↗
The effects of prodipine and budipine on 14C-5-hydroxytryptamine uptake and release by human blood platelets.
The in vitro uptake and release of 14C-5-hydroxy-tryptamine (14C-5-HT) by human blood platelets was examined, which were used in this study as a simple model for serotonergic nerve endings. Experimental conditions allowed measurement of initial velocity of uptake and excluded possible (re)uptake of recently liberated 14C-5-HT in the release studies. The effects of two new antiparkinson drugs, 1-isopropyl-4,4-diphenylpiperdine (prodipine) and its 1-tert-butyl analogue (budipine), on the two opposite transport processes of serotonin were investigated. Prodipine and budipine inhibit the uptake of 14C-5-HT by human blood platelets in a dose-dependent manner. Inhibition of uptake by both drugs is non-competitive; Ki values are 1.1X10(-4) mol/l for prodipine and 9X10(-5) mol/l for budipine, with prodipine additionally showing an effect on Km of serotonin for uptake system. Both substances liberate recently accumulated 14C-5-HT from the platelets. Stimulation of this process is dose-dependent, budipine proving more active than prodipine, both drugs being 5.4 and 4.1 times stronger than amantadine. The observed effects of prodipine and budipine on uptake and release of 14C-5-HT by isolated blood platelets are discussed in the light of other pharmacological activities and the antiparkinson efficacy of these drugs.
Adult↗
The expression of glycoproteins on single blood platelets from healthy individuals and from patients with congenital bleeding disorders.
Glycoproteins present on the surface of blood platelets are fundamental to normal blood platelet behaviour. We have used monoclonal antibodies and flow cytofluorimetry to study the expression of glycoproteins on single platelets from normal subjects, and from patients with Glanzmann's thrombasthenia and the Bernard-Soulier syndrome. We show that normal platelets are heterogeneous in that individual cells display markedly different numbers of glycoprotein IIb/IIIa complex and glycoprotein Ib molecules. We also show that the two congenital bleeding disorders are associated with markedly reduced numbers of glycoprotein IIb/IIIa complex or glycoprotein Ib molecules on all the platelets rather than the difference residing in a sub-population.
Blood Platelets↗
Modulation of cisplatin toxicity in blood platelets by glutathione depletion.
The effect of a specific inhibitor of gamma-glutamylcysteine synthetase, L-buthionine sulfoximine (BSO), on the action of cisplatin in pig blood platelets was investigated. We show that the effect of BSO, blocking glutathione (GSH) synthesis, on depletion of GSH level in platelets was time and dose dependent (p<0.05). Exposure of blood platelets to BSO reduced not only the cellular GSH content, but diminished also cytotoxicity effects of cisplatin on platelets. Cytotoxic effects of cisplatin were determined by the extent of oxidative stress in these cells, i.e. lipid peroxidation expressed as thiobarbituric acid reactive substances and oxygen free radicals (superoxide anion). The obtained results confirm that the intracellular level of GSH plays an important role in the action of cisplatin on blood platelets.
Animals↗
Adhesion of thrombin-stimulated and unstimulated blood platelets to collagen in the presence of Proteus mirabilis lipopolysaccharides.
Adhesion of blood platelets to collagen may be involved in pathogenesis of septic shock after damage of endothelial cells by LPS or inflammatory cytokines. Therefore, analysis of platelet adhesion in the presence of endotoxin seems to be of great importance. We studied in vitro the effects of LPSs (S1959, R110, R45) from Proteus mirabilis (smooth and rough types differing significantly in their composition) on the adhesion of unstimulated and thrombin-stimulated platelets to collagen. The adhesion was measured by a static method as absorbance of cell attached proteins. In this work we report that adhesion of resting platelets to collagen was stimulated by all tested LPSs. The effects were dependent on the doses of LPSs. In the presence of LPSs the inhibition of adhesion of thrombin-treated platelets to collagen was observed. The results presented in this paper indicate that LPSs from Proteus mirabilis may act directly on blood platelets and stimulate adhesion of resting platelets to collagen. On the other hand, LPSs can have an inhibitory effect on adhesion of thrombin-stimulated platelets to collagen.
Animals↗