Effects of Cephalothin and Penicillin G on Platelet Function in Vitro

High concentrations of cephalothin or penicillin G inhibit a number of the functions of human or rabbit platelets in citrated platelet-rich plasma (PRP) and in suspensions of washed platelets. The reactions shown to be inhibited are: ADP-induced shape change and the primary and secondary phases of aggregation and release induced by ADP or adrenaline in human citrated PRP; release and aggregation of washed human platelets exposed to collagen, thrombin, vasopressin, or the ionophore A23,187; aggregation of washed human platelets exposed to phytohaemagglutinin from Phaseolus vulgaris (PHA) or polylysine; release induced by concanavalin A or PHA in suspensions of washed platelets from rabbits; platelet adherence to a collagen-coated surface or to the damaged intimal surface of the rabbit aorta; platelet factor 3 availability; lysis of rabbit platelets by an antiserum directed against them; and clot retraction. Neither antibiotic affected serotonin-induced aggregation; a high concentration of cephalothin slightly inhibited the initial rate of serotonin uptake. Penicilloic acid showed about half the inhibitory effect of penicillin G on ADP-induced aggregation. In citrated human platelet-rich plasma, ampicillin and oxacillin inhibited ADP-induced aggregation to the same extent as similar concentrations of penicillin G; in suspensions of washed platelets, however, ampicillin was less inhibitory than penicillin G or oxacillin. Platelet ultrastructure, assessed by transmission electron microscopy, was not visibly altered. Evidence that the antibiotics become bound to platelets is the finding that platelets incubated with the antibiotics and resuspended in fresh media showed less response to aggregating agents compared with control platelets. Penicillin G and related antibiotics may be inhibitory because they coat the platelet surface. Their effects on platelet functions are probably responsible for excessive bleeding and increased bleeding times observed in patients and volunteers receiving high doses of these antibiotics.     

Metabolism and Function of Human Platelets Washed by Albumin Density Gradient Separation

A method for washing platelets by albumin density gradient separation, originally designed for the study of platelet coagulant activities, has been modified for platelet aggregation and metabolic studies. Platelets are sedimented into a continuous density gradient of isosmolar albumin containing apyrase to protect them from clumping and physical injury and are resuspended in calcium-free Tyrode's solution. The mean recovery of platelets after two separations relative to plateletrich plasma (PRP) was 90.3%. When small amounts of plasma were added to washed platelet suspensions, aggregation and release of [¹⁴C]5-hydroxytryptamine (5HT) in response to adenosine diphosphate (ADP) or 5HT were similar to results obtained with PRP. When fibrinogen was substituted for plasma, ADP-induced aggregation occurred but was feeble. Without added plasma or fibrinogen, platelets were refractory to ADP and insensitive to the cyclic endoperoxide analogue U44619. When both ADP and U44619 were added simultaneously, in low concentrations, to washed platelets without added plasma or fibrinogen, aggregation occurred immediately. Washed platelets were not aggregated by adrenaline, which potentiated ADP-induced aggregation. Several biochemical measurements which are sensitive indicators of cellular damage were normal in washed platelets, including [¹⁴C]adenine uptake, adenylate energy charge, hypoxanthine formation and the response of adenylate cyclase to stimulation by PGE₁ or PGD₂. Platelet coagulant activities were not made available and heparin-neutralizing activity (HNA) was not spontaneously released by the washing procedure, but the washed platelets responded normally to appropriate agents by developing coagulant activities and releasing HNA. The ultrastructure of washed platelets was similar to those in control PRP. Inclusion of apyrase in the first albumin gradient had a beneficial effect on platelet morphology, aggregation and metabolism, but washing at 37deg;C compared with 25deg;C did not. Albumin density gradient separation is a useful method for isolating platelets for aggregation and metabolic studies.     

ADP-Induced Aggregation of Washed Platelets Effect of Platelet and Plasma Fibrinogen

ADP-induced aggregation of washed human and porcine platelets has been studied. Plasma from a patient genetically deficient in fibrinogen lacked ADP-cofactor activity. Apyrase totally inhibited the small platelet aggregation observed after addition of fibrinogen to washed platelets. Lysates of washed porcine platelets contained 1.34 mg/10⁹ platelets of protein in the soluble form and 0.44 mg/10⁹ platelets as insoluble protein. Platelet fibrinogen in soluble fraction was 0.16 mg/10⁹ platelets. Partly purified porcine platelet fibrinogen showed cofactor activity for ADP-induced aggregation of washed porcine platelets, but compared to plasma fibrinogen a higher concentration of the platelet fibrinogen was needed to obtain the same effect.     

Vitamin E reduces platelet adhesion to human endothelial cells in vitro

Although it has been reported that vitamin E (alpha-tocopherol) can reduce platelet adhesiveness and aggregation in vivo, the mechanism is still unknown. Therefore, the aim of the present study was to determine whether incubations of platelet-rich plasma (PRP) with vitamin E influence platelet adhesion to cultured endothelial cells. To exclude blood plasma involvement, also washed platelets were pretreated with alpha-tocopherol. Vitamin E (0.5-1.0 mM) was added to PRP or washed platelets. Endothelial cells in monolayer were incubated with thrombin-activated platelets (1 or 2 U/ml). After 1 hr of incubation, non-adhered platelets were removed and counted. Treating of PRP with alpha-tocopherol inhibited platelet adhesion to endothelial cell monolayer. This effect was dose dependent on concentrations of alpha-tocopherol and thrombin. In our experiments PRP was treated with alpha-tocopherol and endothelial cell monolayer was used as test surface. These findings agree with previous observations on the adhesivity of platelets to synthetic surfaces after dietary vitamin E in healthy volunteers. When washed platelets were incubated with alpha-tocopherol, no significant reduction of adhesion was detectable. As preincubation of washed platelets with alpha-tocopherol does not inhibit platelet adhesion, it may be supposed that the effect of vitamin E does not occur in a directly cellular mechanism. The data suggest that alpha-tocopherol may reduce platelet adhesiveness probably after incorporation by plasma lipoproteins.     

Diurnal variation in melatonin effect on adenosine triphosphate and serotonin release by human platelets

The effect of the pineal hormone melatonin on adenosine diphosphate-induced human platelet aggregation and adenosine triphosphate release was assessed in platelet-rich plasma obtained from normal volunteers at 08.30 and 20.30 h. In 10(-7)-10(-5) mol/l concentrations melatonin inhibited ADP-induced platelet aggregation only in the evening (p less than 0.05). ADP-induced ATP release, an index of platelet secretory processes, showed a generally greater, dose-dependent inhibition after adding melatonin (10(-9)-10(-5)mol/l) at 20.30 h as compared with 08.30 h. The inhibitory activity of melatonin (10(-9)-10(-5) mol/l) on [3H]serotonin release elicited by thrombin in washed human platelets obtained from normal volunteers was dose-dependent; the effect was generally greater at 20.30 h. The activity of the potent platelet anti-aggregating agent prostacyclin did not exhibit diurnal differences with respect to impairing ADP-induced platelet-rich plasma aggregation. These results indicate the existence of a diurnal variation of sensitivity to melatonin in human platelets.     

Evidence that Endotoxins Enhance the Factor X Activator Activity of Washed Human Platelets

The in vitro effect of several bacterial endotoxins on human platelets was determined. Nine different endotoxins failed to induce aggregation in platelet-rich plasma (PRP) or of platelets washed by two different methods; four of them which we studied further failed to induce [14C]serotonin release in PRP. In contrast, using recently described test systems for platelet coagulant activity, all the endotoxins shortened the latent period occurring before aggregation of a mixture of washed platelets, normal serum, and CaCl2, and the clotting time of this mixture upon addition of fibrinogen. Washed platelets obtained from PRP preincubated with endotoxin had a higher platelet coagulant activity than platelets obtained from PRP preincubated with buffer. Washed platelets contribute to thrombin generation by providing factor V, a factor X activator and possibly phospholipid. Since the endotoxins did not influence the factor V activity of platelets or the platelet factor 3 activity, either in PRP or using platelets washed by albumin density gradient centrifugation, it is suggested that they enhance the factor-X activator activity of human platelets.     

Inhibition of human platelet aggregation by the proteolytic effect of streptokinase. Role of the human factor-VIII-related protein.

Defective ADP-induced aggregation was observed in in vitro streptokinases(SK)-treated normal platelet-rich plasma. Classic haemophilia and normal platelet poor plasma (PPP) treated with SK inhibit the aggregation of washed platelets; plasmin-treated normal human serum also shows an inhibitory effect on platelet aggregation. However, SK-treated von Willebrand plasmas do not inhibit the aggregation of washed platelets. This confirms the fact that the anti-aggregating effect is mainly linked to the digested factor VIII) but not to the digested fibrinogen. Defective ristocetin-induced platelet aggregation has also been observed in SK-treated plasmas. The presence of normal PPP does not modify the inhibition of the ADP-induced aggregation of washed platelets in SK-treated PPP. However, it does correct the ristocetin-induced aggregation. These results suggest that the inhibition of the ADP-induced aggregation is caused by the factor VIII degradation products, while the inhibition of the ristocetin-induced aggregation appears because of a defective von Willebrand activity of the factor VIII molecule.     

Inhibition of platelet aggregation by idebenone and the mechanism of the inhibition

The inhibitory effect of 6-(10-hydroxydecyl)-2,3-dimethoxy-5-methyl-1,4-benzoquinone (idebenone) on platelet aggregation was studied in rat and human platelets in vitro, and the mechanism of inhibition was examined in rat platelets. Idebenone inhibited the aggregation induced by collagen and thrombin in washed platelets, and by arachidonate and ADP in platelet-rich plasma (PRP). The inhibition was more prominent in collagen- and arachidonate-induced aggregation. In collagen-induced aggregation of human platelets, idebenone was 8-fold more potent than aspirin. In addition, idebenone inhibited prostaglandin synthesis and thromboxane B2 production, and also increased the cyclic AMP content in platelets. However, the concentration of idebenone required to inhibit thromboxane B2 production was much lower than that required to increase cyclic AMP. These results indicate that idebenone inhibits platelet aggregation by inhibiting thromboxane B2 synthesis rather than by increasing cyclic AMP content.     

Effects of α-tocopherol (Vitamin E) on the Ultrastructure of Human Platelets In Vitro

Washed human platelets were incubated with increasing concentrations of α-tocopherol. Spontaneous aggregation was induced by tocopherol (0.5 mM or above). Aggregation was inhibited by ethylenediaminetetraacetate and platelet activation was reduced by prostaglandin E(1). Using electron microscopy, it was confirmed that tocopherol caused platelet disruption to some extent and the released components may have generated aggregation. These effects were not observed in platelet-rich plasma. Spontaneous activation was not observed when the concentration of tocopherol was 0.03 mM or lower. Concentrations of tocopherol between 0.075 mM and 0.0075 mM had inhibiting influences on activation of washed platelets by thrombin. Tocopherol (between 0.1 mM and 0.005 mM) changed activation of washed platelets by cationized ferritin in that it facilitated the first phase of aggregation but reduced the second phase in an indirect proportional manner. The results show that the effects of tocopherol in washed platelet preparations are not comparable to those observed in plasma and that the platelet membrane must be regarded as a crucial target for vitamin E.     

血小板聚集初期形状变化与聚集的关系及其影响因素分析

目的探讨血小板聚集初期形状改变与聚集的关系,并分析其影响因素。方法制备小鼠、大鼠富血小板血浆（PRP）和人洗涤血小板,以生理盐水、贫血小板血浆（PPP）或Tyrode液调整血小板计数来建立不同的血小板体系,二磷酸腺苷（ADP）或胶原诱导聚集,光学法测定血小板形状变化指标（最大负值和达最大负值时间）以及最大聚集率。结果人的最大负值、达最大负值时间比小鼠增加（P均〈0.05）,最大负值比大鼠增加（P〈0.01）;大鼠达最大负值时间比小鼠增加（P〈0.01）。生理盐水稀释人PRP比PPP稀释人PRP最大负值减小,达最大负值时间延长（P均〈0.05）。在人PRP中,胶原所致最大负值比ADP减小（P〈0.05）,达最大负值时间增加（P〈0.01）;在人洗涤血小板中,胶原所致最大负值、达最大负值时间均比ADP增大（P均〈0.01）;ADP和胶原在洗涤血小板中比PRP中的最大负值、达最大负值时间（除应用胶原变大外）减小（P均〈0.01）。多元回归分析显示,聚集率与最大负值和达最大负值时间正相关（r分别为0.49、0.48,P均〈0.01）。结论血小板聚集初期变形促进聚集,人的比大鼠、小鼠增强,生理盐水稀释PRP和洗涤血小板减弱,在PRP中胶原比ADP所致变形减弱,在洗涤血小板中增强。     

Activation of human platelets by immune complexes prepared with cationized human IgG

The present study shows that the ability of soluble immune complexes (IC), prepared with human IgG and rabbit IgG antibodies against human IgG, to trigger platelet activation was markedly higher for IC prepared with cationized human IgG (catIC) compared with those prepared with untreated human IgG (cIC). CatIC induced platelet aggregation and adenosine triphosphate release in washed platelets (WP), gel-filtered platelets (GFP), or platelet-rich plasma (PRP) at physiologic concentrations of platelets (3 x 10(8)/mL) and at low concentrations of catIC (1 to 30 micrograms/mL). On the contrary, under similar experimental conditions, cIC did not induce aggregation in PRP, WP, or GFP. Low aggregation responses were only observed using high concentrations of both WP (9 x 10(8)/mL) and cIC (500 micrograms/mL). Interestingly, catIC were also able to induce platelet activation under nonaggregating conditions, as evidenced by P-selectin expression. Cationized human IgG alone did not induce platelet aggregation in PRP but triggered either WP or GFP aggregation. However, the concentration needed to induce these responses, was about eightfold higher than those required for catIC. The responses induced either by catIC or cationized human IgG were completely inhibited by treatment with heparin, dextran sulphate, EDTA, prostaglandin E1, or IV3, a monoclonal antibody against the receptor II for the Fc portion of IgG (Fc gamma RII). The data presented in this study suggest that IgG charge constitutes a critical property that conditions the ability of IC to trigger platelet activation.     

Original Article: Cyclosporine a and FK 506 Affect Platelet Functions in Vitro

Cyclosporine A (CyA) is known to be associated with an increased risk of thrombotic complications, whereas FK 506 therapy is believed to cause vasculitis. The aim of the study was to evaluate platelet aggregation in platelet rich plasma (PRP) and in whole blood and ATP release in healthy volunteers. CyA added in different concentrations resulted in a dose-dependent enhancement in platelet response to different agonists in PRP, whereas FK 506 did not influence platelet aggregation when added at a concentration of 2 ng/ml. Preincubation with FK 506 at concentrations of 15 and 50 ng/ml significantly inhibited platelet response to serotonin and epinephrine. Preincubation with both CyA and FK 506 did not affect platelet aggregation either in PRP or in whole blood. CyA at every concentration studied resulted in dose-dependent enhancement in ADP-induced platelet aggregation in whole blood, whereas platelet responses to other agonists were found to be increased only with the highest concentration of CyA together with ATP release. FK 506 (50 ng/ml) resulted in a significant decline in platelet aggregation, whereas lower concentrations did not affect platelet aggregatory responses. Platelet hyperreactivity in response to CyA may contribute, at least in part, to the increased incidence of thrombosis events. Platelet effects of FK 506 in vivo are not yet known, whereas in vitro this drug seems to inhibit aggregation of normal human platelets.     

The effect of oxidatively modified low-density lipoproteins on platelet aggregability and membrane fluidity

The influence of oxidised low-density lipoproteins (oxLDL) on blood cell functions plays a role in the progression of atherosclerosis. In the present work the effects of mildly oxidised LDL (moxLDL) on platelet aggregability and plasma membrane fluidity were studied and analysed from the viewpoint of the extent of LDL oxidation. Native or oxidised LDL were incubated with platelet rich plasma (PRP) at the volume ratio 1:1. As a control, plasma was incubated with buffer. The effects on ADP-induced platelet aggregation and certain membrane characteristics are described. (1) Mildly oxidised LDL diminished the time-dependent decrease in platelet aggregability that was observed when PRP was incubated with buffer or native LDL. The higher the oxidation extent of moxLDL, the lesser (if any) decrease in platelet activity occurred. Therefore moxLDL activated platelets in PRP. Cu2+-oxidised LDL, characterised by a high extent of lipid oxidation, inhibited ADP-induced platelet aggregation. (2) Comparison of the ESR spectra of spin-labelled fatty acid (5-doxylstearate) incorporated into the plasma membrane of washed platelets indicated that the presence of moxLDL in the incubation medium resulted in a reduced fluidity of the outer membrane layer. The cholesterol:phospholipid ratio in platelets appeared to be the same after PRP incubation with native LDL, moxLDL or buffer. It may be proposed that the binding of oxLDL to the platelet surface leads to a modification of the membrane fluidity, thus mediating the activating action of LDL on platelets. Both effects were proportional to the extent of lipid oxidation in LDL. The results of this paper indicate a crucial role for mildly oxidised LDL in platelet activation.     

Original Article: Cyclosporine a and FK 506 Affect Platelet Functions in Vitro

Cyclosporine A (CyA) is known to be associated with an increased risk of thrombotic complications, whereas FK 506 therapy is believed to cause vasculitis. The aim of the study was to evaluate platelet aggregation in platelet rich plasma (PRP) and in whole blood and ATP release in healthy volunteers. CyA added in different concentrations resulted in a dose-dependent enhancement in platelet response to different agonists in PRP, whereas FK 506 did not influence platelet aggregation when added at a concentration of 2 ng/ml. Preincubation with FK 506 at concentrations of 15 and 50 ng/ml significantly inhibited platelet response to serotonin and epinephrine. Preincubation with both CyA and FK 506 did not affect platelet aggregation either in PRP or in whole blood. CyA at every concentration studied resulted in dose-dependent enhancement in ADP-induced platelet aggregation in whole blood, whereas platelet responses to other agonists were found to be increased only with the highest concentration of CyA together with ATP release. FK 506 (50 ng/ml) resulted in a significant decline in platelet aggregation, whereas lower concentrations did not affect platelet aggregatory responses. Platelet hyperreactivity in response to CyA may contribute, at least in part, to the increased incidence of thrombosis events. Platelet effects of FK 506 in vivo are not yet known, whereas in vitro this drug seems to inhibit aggregation of normal human platelets.     

Inhibitory effect of Ginkgo biloba extract on human platelet aggregation

The effect of pure flavonoids and Gingko biloba extract (GBE) on human platelet aggregation was investigated. Most of the flavonoids and vitamin E did not affect platelet aggregation in platelet-rich plasma (PRP); however some of these flavonoids inhibited platelet aggregation in gel-filtered platelets (GFP). GBE inhibited both ADP- and collagen-induced platelet aggregation in PRP, GFP and in whole blood in a dose-dependent manner. GBE at very low concentrations inhibited whole blood aggregation induced by ADP compared with those used for PRP or GFP. Flavonoids and GBE decreased the production of TxA(2) induced by collagen and ADP in PRP. However, no correlation was observed between the inhibition of platelet aggregation and the decrease of TxA(2) synthesis. GBE and flavonoids did not affect platelet membrane fluidity. However, the incubation of PRP with GBE increased cAMP levels in platelets, which is known to inhibit platelet activation by lowering intracellular Ca2+ levels. GBE is a mixture of many compounds, including flavonoids and gingkoglides, which affect metabolism of cAMP, TxA(2) and Ca2+ in platelets. It is effective in the inhibition of platelet aggregation, both in PRP and whole blood, and thus may be potentially used as an effective oral anti-platelet therapeutic agent.     

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

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.     

Inhibition of human platelet aggregation and thromboxane-B2 production by melatonin: evidence for a diurnal variation

The effects of melatonin on platelet aggregation and thromboxane-B2 (TxB2) production induced by 1-4 x 10(-6) M adenosine diphosphate (ADP) or 0.6 x 10(-3) M arachidonic acid (AA) were assessed in platelet-rich plasma (PRP). Micromolar concentrations of melatonin inhibited in a dose-dependent way ADP-induced platelet aggregation with individual inhibitions 40% or more at 10(-6)-10(-5) M. A significant depression of AA-induced platelet aggregation was observed only at 10(-5)-10(-4) M melatonin. Morning (0830 h)-evening (1800 h) studies of ADP-induced platelet aggregation in seven normal men showed a higher sensitivity at 1800 h when analyzed as a global inhibitory effect of melatonin (P less than 0.01). Moreover, only during the evening hours did melatonin induce reversible aggregation, an index of inhibition of the platelet secretory process elicited by ADP exposure. No diurnal variability in melatonin inhibition of AA-induced aggregation was detected. TxB2 production elicited by AA in the evening was inhibited significantly in a concentration-related manner by a 2-min preincubation with 10(-9)-10(-5) M melatonin, while during the morning hours the inhibition was significant only at 10(-6) M or higher melatonin concentrations. In the case of ADP, the inhibition of TxB2 release attained significance at 10(-5)-M (0830 h) or 10(-6)-M concentrations (1800 h). In the presence of either stimulatory agent, melatonin depression of TxB2 generation was about 2-fold greater at 1800 h than at 0830 h. The diurnal changes in melatonin effect on TxB2 production were also observed in thrombin-stimulated washed platelets. The present data indicate the existence of circadian variations in platelet responsiveness to melatonin in humans.     

Platelet aggregation and intracellular calcium mobilisation responses are enhanced by cyclosporin A but not by pimecrolimus (SDZ ASM 981)

It has been shown previously that cyclosporin A enhances platelet aggregation responses, particularly to adenosine diphosphate (ADP). In this investigation platelet responses to ADP in the presence of cyclosporin A and pimecrolimus (SDZ ASM 981), a new cell selective inhibitor of inflammatory cytokines, were determined. Measurements were performed in whole blood using a sensitive platelet counting method and in platelet-rich plasma (PRP) using a Biola laser aggregometer. The latter monitors both aggregate formation and aggregate size. In vitro studies were performed using recombinant hirudin as anticoagulant in order that physiological concentrations of divalent cation concentrations were maintained. Studies using both methods confirmed an enhanced aggregation response to ADP in the presence of cyclosporin A. In contrast, aggregation responses were not enhanced in the presence of pimecrolimus, either in PRP or in whole blood where a slight reduction of ADP-induced aggregation was seen at concentrations of pimecrolimus >10(-6) M. The effects of cyclosporin A and pimecrolimus on ADP-induced calcium mobilisation in platelets were determined using a flow cytometric method. A significant increase in intracellular calcium mobilisation was seen in the presence of cyclosporin A but not in the presence of pimecrolimus. Enhanced platelet aggregation responses to ADP observed in the presence of cyclosporin A may be a consequence of enhanced ADP-induced calcium mobilisation.     

Albumin Density Gradient Separation and Washing of Platelets and the Study of Platelet Coagulant Activities

Summary: Platelets were centrifuged into a specific gravity gradient made by mixing the interface between platelet rich plasma (PRP) and a 40–45% aqueous solution of bovine albumin. By this method of albumin density gradient separation (ADGS) it was possible to centrifuge platelets without disruptive squashing upon a hard surface. The separated platelets were washed in calcium-free Tyrode's solution without releasing coagulant activity. Platelet yields after multiple washings were high. Morphology and ADP-induced aggregation of platelets washed by ADGS (in contrast to platelets washed by conventional methods) were indistinguishable from those of unwashed platelets tested as PRP.
The activities of factors V and XI remained in close association with platelets after four successive washes by ADGS, whereas factors VIII, IX and XII were entirely removed.     

Effect of nicotine on rabbit blood platelet aggregation

Nicotine did not induce platelet aggregation nor potentiate ADP-induced aggregation in rabbit citrated platelet-rich plasma, but did inhibit ADP-induced aggregation when added before ADP, and did reverse ADP-induced aggregation when added after ADP. In contrast to results obtained with human platelets, this latter effect of nicotine was not inhibited by adrenaline in rabbit platelets.