Structurally Diverse Metal Coordination Compounds, Bearing Imidodiphosphinate and Diphosphinoamine Ligands, as Potential Inhibitors of the Platelet Activating Factor

Metal complexes bearing dichalcogenated imidodiphosphinate[R2P(E)NP(E)R2′]-ligands (E = O, S, Se, Te), which act as (E,E) chelates, exhibit a remarkable variety of three-dimensional structures. A series of such complexes, namely, square-planar[Cu{(OPPh2)(OPPh2)N-O,O}2], tetrahedral[Zn{(EPPh2)(EPPh2)N-E,E}2], E = O, S, and octahedral[Ga{(OPPh2)(OPPh2)N-O,O}3], were tested as potential inhibitors of either the platelet activating factor (PAF)- or thrombin-induced aggregation in both washed rabbit platelets and rabbit platelet rich plasma. For comparison, square-planar[Ni{(Ph2P)2N-S-CHMePh-P,P}X2], X = Cl, Br, the corresponding metal salts of all complexes and the(OPPh2)(OPPh2)NHligand were also investigated.Ga(O,O)3showed the highest anti-PAF activity but did not inhibit the thrombin-related pathway, whereasZn(S,S)2, with also a significant PAF inhibitory effect, exhibited the highest thrombin-related inhibition.Zn(O,O)2andCu(O,O)2inhibited moderately both PAF and thrombin, being more effective towards PAF. This work shows that the PAF-inhibitory action depends on the structure of the complexes studied, with the bulkierGa(O,O)3being the most efficient and selective inhibitor.

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Effects of Ethanol on Pathways of Platelet Aggregation In Vitro

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647500 ◽

1988 ◽

Vol 59 (03) ◽

pp. 383-387 ◽

Cited By ~ 42

Author(s):

Margaret L Rand ◽

Marian A Packham ◽

Raelene L Kinlough-Rathbone ◽

J Fraser Mustard

Keyword(s):

Arachidonic Acid ◽

Platelet Aggregation ◽

Platelet Rich Plasma ◽

Secondary Phase ◽

Primary Phase ◽

Rabbit Platelet ◽

Membrane Phospholipids ◽

Rabbit Platelets ◽

Induced Aggregation

SummaryEthanol, at physiologically tolerable concentrations, did not affect the primary phase of ADP-induced aggregation of human or rabbit platelets, which is not associated with the secretion of granule contents. Potentiation by epinephrine of the primary phase of ADP-induced aggregation of rabbit platelets was also not inhibited by ethanol. However, ethanol did inhibit the secondary phase of ADP-induced aggregation which occurs with human platelets in citrated platelet-rich plasma and is dependent on the formation of thromboxane A2. Inhibition by ethanol of thromboxane production by stimulated platelets is likely due to inhibition of the mobilization of arachidonic acid from membrane phospholipids, as ethanol had little or no effect on aggregation and secretion induced by arachidonic acid or the thromboxane mimetic U46619. Rabbit platelet aggregation and secretion in response to low concentrations of collagen, thrombin, or PAF were inhibited by ethanol. Inhibition of the effects of thrombin and PAF was also observed with aspirin-treated platelets. Thus, in addition to inhibiting the mobilization of arachidonate for thromboxane formation that occurs with most agonists, ethanol can also inhibit aggregation and secretion through other effects on platelet responses.

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The Role of Prostaglandins in the ADP-Induced Aggregation of Rabbit Platelets Shown by the Use of 15-Hydroxyprostaglandin Dehydrogenase

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646749 ◽

1978 ◽

Vol 39 (03) ◽

pp. 725-732 ◽

Cited By ~ 2

Author(s):

Robert B Wallis

Keyword(s):

Platelet Rich Plasma ◽

Shape Change ◽

Rabbit Platelet ◽

Direct Role ◽

Initial Shape ◽

Rabbit Platelets ◽

Induced Aggregation ◽

Aggregation Of Platelets

SummaryThe initial shape change and subsequent aggregation of platelets in citrated rabbit platelet-rich plasma caused by ADP in vitro was inhibited by 15-hydroxyprostaglandin dehydrogenase. This inhibition was NAD-dependent and was also seen when shape change and aggregation were initiated by sodium arachidonate or by collagen. The aggregation of gel-filtered rabbit platelets by thrombin was not, however, affected by removal of 15-hydroxyprostaglandins.Indomethacin was found to inhibit ADP-induced aggregation but at a concentration (250 μM) much higher than that required to inhibit collagen-induced aggregation. Moreover the platelet release reaction had not taken place 3 min after ADP stimulation. The direct role 15-hydroxyprostaglandin production in ADP-induced aggregation of rabbit platelets is proposed. The involvement of 15-hydroxyprostaglandins in platelet aggregation caused by other inducers is also discussed.

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ETHANOL INHIBITS RABBIT PLATELET RESPONSES TO COLLAGEN IN VITRO BUT DOES NOT AFFECT RABBIT PLATELET ADHERENCE TO DE-ENDOTHELIALIZED A0RTAE IN VIVO

10.1055/s-0038-1643547 ◽

1987 ◽

Author(s):

M L Rand ◽

H M Groves ◽

R L Kinlough-Rathbone ◽

M A Packham ◽

J F Mustard

Keyword(s):

Coronary Heart Disease ◽

Heart Disease ◽

Ex Vivo ◽

Platelet Rich Plasma ◽

Inhibitory Effect ◽

Rabbit Platelet ◽

Platelet Adherence ◽

Induced Aggregation

Epidemiological studies indicate that moderate consumption of alcohol is associated with a reduced risk of coronary heart disease, but it is not known whether inhibition of platelet functions by ethanol is involved. We studied the effects of ethanol on rabbit platelet responses to collagen in vitro and in vivo. Addition of ethanol (4 mg/ml) to suspensions of washed platelets prelabelled with [14c]serotonin inhibited aggregation and secretion in response to low (0.4 μg/ml) concentrations of acid soluble collagen (14% secretion without ethanol, 3% secretion with ethanol). With a higher concentration of collagen (1.25 μg/ml), 4 mg/ml ethanol had no inhibitory effect. The inhibitory effect of ethanol on collagen-induced aggregation was also observed in citrated platelet-rich plasma (c-PRP) to which ethanol was added in vitro and in c-PRP from rabbits given ethanol acutely by gavage (3.5 g/kg) 30 min before blood sampling. The accumulation of [51cr]-labeled platelets on the subendothelium of rabbit aortae de-endothelialized with balloon catheters was measured in vivo in rabbits given ethanol (blood ethanol concentration at time of vessel wall injury: 4.1 ± 0.2 mg/ml, mean ± S.E., n=6). Ten min after de-endothelialization, there was no difference between the number of platelets adherent per square mm of injured aorta of control rabbits (39,400 ± 2,600, mean ± S.E., n=6) and intoxicated rabbits (36,800 ± 3,700, mean ± S.E., n=6). Thus, although ethanol inhibits platelet aggregation and secretion in response to collagen in vitro and ex vivo, it does not alter platelet adherence to the subendothelium, including its constituent collagen, in vivo. Therefore, it is unlikely that ethanol exerts its beneficial effects against coronary heart disease by altering the initial adherence of platelets to injured vessel walls.

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Phospholipase C from Clostridium Perfringens Induces Human Platelet Aggregation in Plasma

Thrombosis and Haemostasis ◽

10.1055/s-0038-1642761 ◽

1988 ◽

Vol 59 (02) ◽

pp. 236-239 ◽

Cited By ~ 2

Author(s):

Giovanna Barzaghi ◽

Chiara Cerletti ◽

Giovanni de Gaetano

Keyword(s):

Platelet Aggregation ◽

Receptor Antagonist ◽

Phospholipase C ◽

Clostridium Perfringens ◽

Human Platelet ◽

Ex Vivo ◽

Platelet Rich Plasma ◽

Platelet Activating Factor ◽

Inhibitory Effect ◽

Thromboxane Receptor Antagonist

SummaryWe studied the aggregating effect of different concentrations of phospholipase C (PLC) (extracted from Clostridium perfringens) on human platelet-rich plasma (PRP). PRP was preincubated with PLC for 3 min at 37° C and the platelet aggregation was followed for 10 min. The threshold aggregating concentration (TAG) of PLC was 3-4 U/ml.We also studied the potentiation of PLC with other stimuli on platelet aggregation. Potentiating stimuli, such as arachidonic acid (AA), ADP. Platelet Activating Factor (PAF) and U-46619 (a stable analogue of cyclic endoperoxides) were all used at subthreshold concentrations. We also studied the possible inhibitory effect of aspirin, apyrase, TMQ, a prostaglandin endoper- oxide/thromboxane receptor antagonist and BN-52021, a PAF receptor antagonist. Only aspirin and apyrase were able to reduce aggregation induced by PLC alone and PLC + AA and PLC + ADP respectively. TMQ and BN-52021 were inactive. In ex vivo experiments oral aspirin (500 mg) partially inhibited platelet aggregation induced by PLC alone, PLC + AA and PLC + ADP 2 and 24 h after administration. Aspirin 20 mg for 7 days also reduced aggregation induced by PLC + AA.

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In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646570 ◽

1989 ◽

Vol 61 (02) ◽

pp. 254-258 ◽

Cited By ~ 21

Author(s):

Margaret L Rand ◽

Peter L Gross ◽

Donna M Jakowec ◽

Marian A Packham ◽

J Fraser Mustard

Keyword(s):

Cyclic Amp ◽

Inhibitory Effect ◽

Rabbit Platelet ◽

Inhibitory Effects ◽

Low Concentrations ◽

Rabbit Platelets ◽

High Concentrations ◽

In Vitro Effects ◽

Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

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Inhibition by Glaucocalyxin A of Aggregation of Rabbit Platelets Induced by ADP, Arachidonic Acid and Platelet-Activating Factor, and Inhibition of [3H]-PAF Binding

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648470 ◽

1992 ◽

Vol 67 (04) ◽

pp. 458-460 ◽

Cited By ~ 12

Author(s):

Zhang Bin ◽

Long Kun

Keyword(s):

Arachidonic Acid ◽

Platelet Aggregation ◽

Platelet Activating Factor ◽

Northeastern China ◽

Ethereal Extract ◽

Ic50 Value ◽

Rabbit Platelets ◽

Ic50 Values ◽

Induced Aggregation

SummaryGlaucocalyxin A is a new diterpenoid isolated from the ethereal extract of the leaves of Rabdosia japonica (Burm f) Hara var glaucocalyx (Maxim) Hara (Labiatae) collected in the northeastern China. When it was incubated with washed rabbit platelets, glaucocalyxin A inhibited ADP- or arachidonic acid-induced platelet aggregation with IC50 values of 4.4 μmol/1, 14.1 μmol/1 respectively. Glaucocalyxin A also inhibited PAF-induced aggregation of rabbit platelets which were refractory to ADP and arachidonic acid with an IC50 value of 13.7 μmol/1. Analysis of [3H]-PAF binding showed that glaucocalyxin A prevented [3H]-PAF binding to intact washed rabbit platelets with an IC50 value of 8.16 μmol/1, which was consistent with its inhibition of PAF-induced platelet aggregation.

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Effects of Bupranolol, a New β-Blocker, on Platelet Functions of Rabbit and Human in Vitro

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648052 ◽

1976 ◽

Vol 36 (02) ◽

pp. 376-387 ◽

Cited By ~ 3

Author(s):

Teruhiko Umetsu ◽

Kazuko Sanai ◽

Tadakatsu Kato

Keyword(s):

Platelet Aggregation ◽

Platelet Adhesion ◽

Human Platelets ◽

Rabbit Platelet ◽

Rabbit Platelets ◽

Β Blocker ◽

Platelet Aggregates ◽

Induced Aggregation ◽

Platelet Functions

SummaryThe effects of bupranolol, a new β-blocker, on platelet functions were investigated in vitro in rabbits and humans as compared with propranolol, a well-known β-blocker. At first, the effect of adrenaline on ADP-induced rabbit platelet aggregation was studied because adrenaline alone induces little or no aggregation of rabbit platelets. Enhancement of ADP-induced rabbit platelet aggregation by adrenaline was confirmed, as previously reported by Sinakos and Caen (1967). In addition the degree of the enhancement was proved to be markedly affected by the concentration of ADP and to increase with decreasing concentration of ADP, although the maximum aggregation (percent) was decreased.Bupranolol and propranolol inhibited the (adrenaline-ADP-)induced aggregation of rabbit platelets, bupranolol being approximately 2.4–3.2 times as effective as propranolol. Bupranolol stimulated the disaggregation of platelet aggregates induced by a combination of adrenaline and ADP, but propranolol did not. Platelet adhesion in rabbit was also inhibited by the β-blockers and bupranolol was more active than propranolol. With human platelets, aggregation induced by adrenaline was inhibited by bupranolol about 2.8–3.3 times as effectively as propranolol.From these findings. We would suggest that bupranolol might be useful for prevention or treatment of thrombosis.

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Inhibition of Human Platelet Aggregation by the Proteolytic Effect of Streptokinase (SK). Role of the Factor VIII Related Antigen

10.1055/s-0039-1689380 ◽

1975 ◽

Cited By ~ 1

Author(s):

R. Castillo ◽

S. Maragall ◽

J. A. Guisasola ◽

F. Casals ◽

C. Ruiz ◽

...

Keyword(s):

Platelet Aggregation ◽

Factor Viii ◽

Platelet Rich Plasma ◽

Gel Filtration ◽

Inhibitory Effect ◽

Factor Viii Related Antigen ◽

Human Factor Viii ◽

Induced Aggregation

Defective ADP-induced platelet aggregation has been observed in patients treated with streptokinase. This same effect appears “in vitro” when adding SK to platelet rich plasma (PRP). Classic hemophilia and normal platelet poor plasmas (PPP) treated with SK inhibit the aggregation of washed platelets; plasmin-treated normal human serum also shows an inhibitory effect on platelet aggregation. However, von Willebrand SK-treated plasmas do not inhibit the aggregation of washed platelets. The same results appear when plasmas are previously treated with a rabbit antibody to human factor VIII.This confirms that the antiaggregating effect is mainly linked to the digested factor VIII related antigen.The inhibition of ADP-induced platelet aggregation has been proved in gel filtration-isolated and washed platelets from SK-treated PRP.Defective ristocetin-induced platelet aggregation has also been observed- This action does not appear in washed platelets from SK-treated PRP in presence of normal PPP, but it does in presence of SK-treated PPP, which suggests that the inhibition of the ristocetin-induced aggregation is due to the lack of factor VIII and not to the factor VIII-related products.Heparin, either “in vivo” or “in vitro”, has corrected the antiaggregating effect of SK.

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EFFECTS OF CELL ADHESION PEPTIDE, Arg-Gly-Asp-Ser (RGDS), ON RESPONSES OF WASHED PLATELETS FROM HUMANS, RABBITS AND RATS

10.1055/s-0038-1643592 ◽

1987 ◽

Author(s):

E J Harfenist ◽

M A Packham ◽

J F Mustard

Keyword(s):

Cell Adhesion ◽

Inhibitory Effect ◽

Human Platelets ◽

Independent Component ◽

Tyrode Solution ◽

Significant Extent ◽

Aggregation Mechanism ◽

Rabbit Platelets ◽

Induced Aggregation ◽

Rat Platelets

Fibrinogen (Fbg) is a cofactor in the aggregation of human platelets, and washed platelets do not aggregate to a significant extent in response to ADP unless Fbg is added to the suspension; however, exogenous Fbg is not required for ADP-induced aggregation of washed platelets from rabbits or rats. Since, with human platelets, Arg-Gly-Asp-Ser (RGDS) inhibits aggregation and the binding of 125I-Fbg to ADP-stimulated platelets, its effects on the responses of rabbit and rat platelets were studied in an attempt to elucidate the differences in Fbg requirements of platelets from the three species. Aggregation and Fbg binding were studied using washed platelets suspended in Tyrode solution containing albumin, apyrase and 2 mM Ca2+. 50 μM RGDS caused over 80% inhibition of the aggregation of human platelets stimulated with 9 yM ADP in the presence of 0.2 yM Fbg, but only 3-9% inhibition of the ADP-induced aggregation of rabbit or rat platelets regardless of whether exogenous Fbg was added. 50 yM RGDS also inhibited the aggregation of human platelets stimulated with thrombin (0.9 U/mL), but produced no more than 3% inhibition with rabbit or rat platelets. The binding of 125I-Fbg to ADP-stimulated human platelets was inhibited by 80-90% by 30 yM RGDS, but even at 50 μM, RGDS inhibited Fbg binding to rabbit or rat platelets by only 15-27%. The differences were due to the species of platelets, since, with both human and rabbit platelets, human Fbg could be replaced by rabbit Fbg without significantly changing the results. RGDS, added to human platelets that had been aggregated with thrombin, did not cause deaggregation, but did partially inhibit aggregation when added within 1 min; this inhibitory effect was less than when RGDS was added before thrombin, and decreased progressively as the length of time before the addition of RGDS was increased. These observations indicate a difference in aggregation mechanism between human platelets and those from rabbits and rats, and are consistent with a Fbg-independent component to the aggregation of rabbit and rat platelets.

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Prostaglandins and Platelet Function in Diabetes

10.1055/s-0039-1687328 ◽

1979 ◽

Author(s):

J. García-Conde ◽

J.A. Amado ◽

J. Merino ◽

I. Benet

Keyword(s):

Platelet Aggregation ◽

Platelet Rich Plasma ◽

Normal Subjects ◽

Inhibitory Effect ◽

Rat Aorta ◽

Diabetic Group ◽

Diabetic Patients ◽

Prostaglandin I2 ◽

Induced Aggregation ◽

Normal Controls

We have studied platelet aggregation induced by 0,5 mM. Araquidonic acid (AA) addition to platelet-rich-plasma (PRP) from 21 insulin treated diabetic patients and in 21 non-diabetic controls. The velocity of aggregation was significantly higher in the diabetic group. There was no differences in the velocity of aggregation in patients with or without retinopathy.The incubation of PRP of normal subjects at 37- during 5 minutes with 5,8 10-4 M. Imidazole changed the pattern of aggregation: The velocity of aggregation was slower and appeared a wave of disaggregation. Imida zole had not effect on aggregation in the diabetic group. This data add support to the findings published by COLWLLL showing that platelets from diabetics have hyperactive AA metabolism. Prostaglandin I2 (PGI2) obtained from rat aorta shows an inhibitory effect on ADP or AA induced aggregation. This effect is less marked in diabetic PRP than in PRP of normal controls. PGI2 release in platelet-poor-plasma from diabetics is normal. This can represent a resistance ot diabetic platelet to the anti aggregating effect of PGI 2. A similar finding was also appreciated with the PGE1 in three out of six patients so tar stu

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