Influence of organotins on rat platelet aggregation mechanisms

The effects of ten organotins on rat platelet aggregation mechanisms were examined. Bis(tri-n-butyltin)oxide was the most potent inhibitor of both ADP- and collagen-induced aggregation, and it was the only organotin that directly induced aggregation. It also increased the latent period for induction of aggregation by collagen. Triphenyltin hydroxide was a weak inhibitor of both ADP- and collagen-induced aggregation. However, in contrast to bis(tri-n-butyltin)oxide, it decreased the latent period for collagen-induced aggregation. A similar effect also was observed with diphenyltin dichloride, phenyltin trichloride, and cyhexatin. Tri-n-butyltin chloride and tetra-n-butyltin demonstrated specificity in their action since aggregation induced by ADP but not collagen was inhibited. Tri-n-propyltin chloride, trimethyltin chloride, and fenbutatin oxide were without discernible effect on rat platelet aggregation.     

Effect of D-003 on intravascular platelet aggregation induced with collagen in rats

D-003 is a mixture of higher aliphatic primary acids purified from sugar-cane (Saccharum officinarum L.) wax that inhibits platelet aggregation induced ex vivo by addition of agonists to platelet-rich plasma (PRP) of rats, guinea pigs, and healthy human volunteers. Because the ex vivo platelet aggregation model does not mimic properly platelet aggregation occurring inside the arteries, since all blood factors regulating the formation of a platelet aggregate or thrombus are not present in PRP, this work was undertaken in order to investigate the effects of different oral doses of D-003 on platelet aggregation induced by collagen in vivo in rats. Effects of single (5, 25, 100, and 200 mg/kg) or repeated doses (1, 5, 25, 100, and 200 mg/kg during 10 days) of D-003 on in vivo platelet aggregation in rats were studied. D-003 (5-200 mg/kg) orally administered as single or repeated doses inhibited significantly and dose-dependently collagen-induced platelet aggregation in rats. The minimal dose investigated effective in both single and repeated administration schemes was 5 mg/kg. The highest dose assessed in both cases was 200 mg/kg, causing inhibitions of 61.5% (single doses) and 74.4% (repeated doses). Thus, the effects of repeated doses were more pronounced than those obtained with single administration. The mean 50% effective dose of D-003 in both schemes was 2.3 mg/kg, which indicates a promising anti-thrombotic potential of D-003.     

Impaired platelet aggregation and thromboxane generation in essential fatty acid-deficient rats

ADP-induced platelet aggregation and thrombin-induced thromboxane B2 generation in diluted whole blood from rats fed a fat-free diet supplemented with 10% (by weight) hydrogenated coconut oil [essential fatty acid (EFA) deficient] were significantly lower than that in animals fed 10% safflower oil [(SFO) rich in linoleic acid] or 10% marine oil (rich in eicosapentaenoic acid and docosahexaenoic acid). Plasma fibrinogen levels were significantly lower and liver function was impaired in the EFA-deficient group compared with the other two groups. Platelet responsiveness to ADP was restored when plasma from the EFA-deficient rats was replaced by plasma obtained from rats fed a nonpurified diet. ADP responsiveness and thrombin-stimulated thromboxane B2 production in diluted whole blood were also restored after 2 wk of injections of 100 mg ethyl linoleate every 48 h, and partially restored by injections of 100 mg ethyl alpha-linolenate. When ADP-induced platelet aggregation was examined in washed platelets, the impaired ADP aggregation (found when platelets of the EFA-deficient rats were suspended in their own plasma) was not observed at either high (9.5 microM) or low (1.0 microM) ADP concentrations. Although thrombin-stimulated thromboxane B2 production in washed platelets in the EFA-deficient rats was lower than that in the SFO-fed rats, the magnitude of aggregation was not different. In addition, inhibition of thrombin-induced platelet aggregation by apyrase (0.06 U/mL) was identical in the two groups. These results suggest that impaired platelet aggregation in EFA deficiency is related more to plasma factors than to inherent platelet properties and that restoration of normal liver function is associated with normal platelet function.(ABSTRACT TRUNCATED AT 250 WORDS)     

阿藿烯对兔血小板聚集抑制作用

目的探讨阿藿烯对家兔血小板聚集作用的影响。方法体外给药,以二磷酸腺苷(ADP)、凝血酶(Thr)作诱导剂,比浊法测定血小板聚集率,观察阿藿烯对血小板聚集的抑制作用及量效关系。结果高、中剂量阿藿烯可降低由ADP所诱导的血小板最大聚集率(P<0.01),血小板聚集抑制率(AIR)可达57%和70%;高、中、低剂量阿藿烯均可降低由Thr所诱导的血小板最大聚集率(P<0.01),AIR分别达49%,81%和87%,作用强度随阿藿烯剂量的增加而增强。结论阿藿烯对由ADP和凝血酶所诱导的血小板聚集具有较强的抑制作用。     

Variations of fatty acid composition in plasma lipids and platelet aggregation in magnesium deficient rats

Control and magnesium deficient rats were pair-fed for 8 days. Deficient animals had higher levels of plasma triglycerides and lower levels of plasma HDL cholesterol than control rats. As compared to controls, Mg deficient rats had decreased levels of stearic acid, increased levels of oleic acid and linoleic acid, and decreased levels of arachidonic acid in total plasma lipids. The fatty acid composition of cholesteryl esters showed higher levels of oleic and linoleic acids, lower levels of arachidonic acid in deficient rats compared to control group. Deficient rats had higher levels of linoleic acid in plasma triglycerides and plasma phospholipids, and lower levels of arachidonic acid in plasma triglycerides whereas no significant variation occurred in the arachidonic content of phospholipids. Thrombin, at a final concentration of 0.25 NIH units per ml of platelet rich plasma, did not produce platelet aggregation in control rats while aggregation did occur in Mg deficient animals. These results indicate that significant alterations in fatty acid metabolism and platelet aggregation occur as a consequence of acute Mg deficiency in the rat.     

The effect of ChAdOx1 nCov-19 vaccine on arterial thrombosis development and platelet aggregation in female rats

ChAdOx1 nCoV-19 adenoviral vector vaccine (ChAd) against coronavirus disease 2019 has been associated with vaccine-induced thrombosis and thrombocytopenia (VITT), especially in young women who have presented with unusual localized thrombosis after receiving the vaccine. The pathogenesis of VITT remains incompletely understood. We tried to provide new insights into mechanisms underlying this phenomenon in the model of arterial thrombosis electrically induced in the carotid artery of female rats. At 28 days post-vaccination, ChAd induced SARS-CoV-2-specific neutralizing antibody responses in all animals. The analysis of the blood vessel/thrombus area showed slight luminal narrowing of the carotid artery with extravasation of blood in vaccinated rats. These small changes were not accompanied by differences in thrombus weight and composition. The vaccinated animals presented a slight increase (by around 14–24%) in platelet aggregation. ChAd did not significantly affect blood coagulation, platelet counts, and their activation markers. Unaffected thrombus formation, the lack of thrombocytopenia and all the measured blood and hemostasis parameters that predominantly stayed unchanged, indicate that the ChAd does not increase the risk of arterial thrombosis development in female rats.     

Taurine modulates platelet aggregation in cats and humans

To explore the relationship between whole-body taurine status and function, the taurine concentration in plasma and platelets was measured and evaluated in terms of ex vivo collagen-induced platelet aggregation in taurine-depleted cats and taurine-supplemented humans. Taurine status exerted a significant effect on platelet aggregability. Platelets from taurine-depleted cats were twice as sensitive to aggregation as platelets from cats receiving taurine. On the other hand, platelets from humans with normal taurine status increased resistance to aggregation by 30-70% when supplemented with taurine at 400 or 1600 mg/d, respectively. Decreased platelet aggregability was associated with increased platelet taurine and glutathione concentrations and decreased thromboxane release on aggregation. These data indicate that taurine in vivo stabilizes platelets against aggregation such that during taurine depletion platelets become overly sensitive whereas during supplementation their tendency to aggregate is depressed.     

Effects of methanol and formic acid on human platelet aggregation

Background

Although ethanol is known to inhibit platelet aggregation, the effects of another variant of alcohol, methanol, have not been reported. The purpose of this study was to determine whether methanol and its metabolite, formic acid, affect Ca²⁺ entry into and subsequent aggregation of platelets in vitro.

Methods

Ca²⁺ entry into and aggregation of human platelets were measured by spectrofluorometry using Fura-2/AM as an indicator and the light transmission method, respectively.

Results

Thrombin-induced platelet aggregation was significantly augmented by methanol at pharmacological concentrations (0.5–2%) in a concentration-dependent manner. Methanol at 2% significantly attenuated thapsigargin-induced platelet aggregation, which was not significantly affected by lower concentrations (0.5 and 1%) of methanol. Methanol (0.5–2%) did not significantly affect platelet aggregation induced by 1-oleoyl-2-acetyl-sn-glycerol (OAG), or Ca²⁺ entry into platelets induced by thrombin, thapsigargin, or OAG. Platelet aggregation induced by thrombin, thapsigargin, or OAG was significantly inhibited by formic acid at toxic concentrations (0.01% or higher). Ca²⁺ entry into platelets induced by thrombin or thapsigargin was also significantly inhibited by formic acid at 0.01% or higher, while that induced by OAG was not affected by formic acid at 0.005 and 0.01% and augmented by that at 0.02%.

Conclusions

Methanol at pharmacological doses has diverse effects on platelet aggregation, depending on the aggregation stimuli, without affecting Ca²⁺ entry into platelets. Formic acid at toxic concentrations has an inhibitory action on platelets aggregation, which was partly explained by the reduction of Ca²⁺ entry into platelets.

     

硝酸甘油对妊高征患者血流变学、血小板聚集的影响

目的:拟用硝酸甘油(Ng)治疗妊高征(PIH),评价其对PIH患者血流变学、血小板聚集的影响。方法:选取晚期正常妊娠妇女(正常组Ⅰ组:11例),中、重度妊高征患者34例[PIH组,其中单用硫酸镁(Mg)治疗Ⅱ组:11例;单用硝酸甘油(Ng)治疗Ⅲ组:11例;联合用药(Mg+Ng)治疗Ⅳ组:12例]。采用血液粘度仪在高、低切变率下测血流变学,硫酸铵沉淀法测纤维蛋白原(Fn),魏式法测血沉(ESR),常规法测红细胞压积(Hct),血小板聚集仪测血小板聚集(PAg)。结果:①血流变学:产前:PIH组较Ⅰ组全血粘度(BV),红细胞聚集指数(RE)、血浆粘度(PV)、Hct、ESR、血沉方程K值(Kesr)、Fn均增高(P<0.05)差异显著;产后各组无明显差别,Ⅲ、Ⅳ组治疗后BV、ESR、Kesr、Fn下降,差异显著(P<0.05),余下指标及Ⅱ组各指标改变不明显。②血小板聚集:产前:PIH组较Ⅰ组增高,差异显著(P<0.05),产后:各组无明显差别;Ⅲ、Ⅳ组治疗后较用前降低,差异显著(P<0.01),Ⅱ组改变不明显。结论:硝酸甘油作为NO供体治疗妊高征时,能改变血流变,抑制血小板聚集。     

硝酸甘油对妊高征患者血流变学、血小板聚集的影响

目的拟用硝酸甘油(Ng)治疗妊高征(PIH),评价其对PIH患者血流变学、血小板聚集的影响.方法选取晚期正常妊娠妇女(正常组Ⅰ组11例),中、重度妊高征患者34例[PIH组,其中单用硫酸镁(Mg)治疗Ⅱ组11例;单用硝酸甘油(Ng)治疗Ⅲ组11例;联合用药(Mg+Ng)治疗Ⅳ组12例].采用血液粘度仪在高、低切变率下测血流变学,硫酸铵沉淀法测纤维蛋白原(Fn),魏式法测血沉(ESR),常规法测红细胞压积(Hct),血小板聚集仪测血小板聚集(PAg).结果①血流变学产前PIH组较Ⅰ组全血粘度(BV),红细胞聚集指数(RE)、血浆粘度(PV)、Hct、ESR、血沉方程K值(Kesr)、Fn均增高(P＜0.05)差异显著;产后各组无明显差别,Ⅲ、Ⅳ组治疗后BV、ESR、Kesr、Fn下降,差异显著(P＜0.05),余下指标及Ⅱ组各指标改变不明显.②血小板聚集产前PIH组较Ⅰ组增高,差异显著(P＜0.05),产后各组无明显差别;Ⅲ、Ⅳ组治疗后较用前降低,差异显著(P＜0.01),Ⅱ组改变不明显.结论硝酸甘油作为NO供体治疗妊高征时,能改变血流变,抑制血小板聚集.     

Effect of oral vitamin B6 supplementation on in vitro platelet aggregation

A randomized, double-blind study was conducted with 12 healthy adult males to determine the effects of oral pyridoxine supplementation on in vitro platelet aggregation. Following a 4-wk baseline period, half the subjects received 100 mg/day of pyridoxine X HCl while the remaining subjects received a placebo for 6 wk. In vitro platelet responses to ADP and collagen and the plasma pyridoxal 5'-phosphate (PLP) concentrations were measured at biweekly intervals. Plasma PLP concentrations increased significantly (p less than 0.001) for those receiving the vitamin B6 compared to baseline values or compared to those receiving the placebo. However, there was no significant effect of increased levels of plasma PLP on collagen-stimulated platelet aggregation and only a slight effect on ADP-stimulated aggregation. Acute administration of 100 mg pyridoxine X HCl failed to alter the in vitro response of platelets to either ADP or collagen. Reevaluation of conclusions based solely on in vitro studies suggesting the use of pyridoxine as an effective in vivo antithrombotic agent may be warranted.     

Dietary fats modulate hormonal contraceptive induced changes in platelet aggregation,composition and lipid biosynthesis in female rats

Female rats were fed purified diets containing 40% fat rich in either saturated (P/S=0.10), or polyunsaturated fatty acids (P/S=0.34). After 17, 34 and 52 weeks, ethynyloestradiol + lynestrenol were given for 4 days in subgroups on both diets, and the 5th day platelet aggregation and lipid biosynthesis, platelet and plasma lipids were studied. While thrombin-induced aggregation was higher (p<.001) in saturated fat fed animals, it was only in rats fed polyunsaturated fat diet that the contraceptive induced an increase of the platelet response to aggregation associated with an an increase in platelet lipid biosynthesis, especially in lanosterol + dihydrolanosterol fractions. The enhanced aggregation induced by saturated fat appears to be related to platelet fatty acids, whereas the one induced by the hormonal contraceptive used here was associated mostly with accumulation of lanosterol in platelets and a fall in plasma vitamin E.     

Effects of taurine on plasma and liver lipids, erythrocyte ouabain sensitive Na efflux and platelet aggregation in Sprague Dawley rats

The effects of taurine on plasma and liver cholesterol, erythrocyte ouabain sensitive Na efflux and platelet aggregation were examined in Sprague Dawley rats fed control or 0.5% cholesterol with 0.2% cholate diet. Plasma and liver levels of total cholesterol were increased significantly (p<0.05) in rats fed cholesterol diet compared to the control, and taurine significantly decreased the elevated plasma level of cholesterol in rats fed cholesterol diet (p<0.05). HDL-cholesterol was decreased in groups fed the cholesterol diet regardless of taurine supplementation and the difference between groups with and without cholesterol was significant (p<0.01). Plasma triglyceride was decreased and liver triglyceride was increased both significantly (p<0.05) in rats fed cholesterol compared to the control. Plasma and liver triglyceride in rats fed taurine was decreased significantly compared to the control (p<0.05). Intracellular Na tended to be lower in rats fed cholesterol or taurine and higher in rats fed cholesterol plus taurine compared to the control. Na efflux through Na-K ATPase and the passive leak of Na was somewhat reduced in rats fed cholesterol or taurine and was augmented in rats fed cholesterol plus taurine compared to the control, which showed a similar trend to the intracellular Na. Taurine supplementation caused a suppression of Na efflux in groups fed control diet and restored the suppressed Na efflux in groups fed cholesterol. Platelet aggregation was significantly decreased in the group fed taurine compared to the control (p<0.05) and the group fed cholesterol plus taurine was also a little lower in aggregation than the group fed cholesterol. Microscopic examination showed that taurine prevented fatty liver in rats fed cholesterol diet. Taurine known for stimulating Na-K ATPase in some cell types rather decreased erythrocyte ouabain sensitive Na-K ATPase in the present study. Taurine had hypolipidemic and hypocholesterolemic effects and inhibited platelet aggregation which may be favorable for prevention of cardiovascular diseases.     

Zinc deficiency and impaired platelet aggregation in guinea pigs

Previous studies have shown that acute zinc deficiency results in impaired platelet aggregation in humans and rats as well as decreased sensitivity to such aggregating agents as ADP, arachidonate and collagen. This study was designed to evaluate the effect of zinc deficiency on platelet function and other pathology in the guinea pig. Guinea pigs of mixed sex were fed a purified diet based on soybean protein (1 ppm Zn) or a similar control diet (100 ppm Zn). In one trial weanling guinea pigs, weighing about 150 g, were fed the diets for 22 days. Those fed the basal diet failed to grow after 2 weeks, and food consumption decreased at this time although it did not become cyclic. They developed skin lesions; zinc concentrations were decreased in plasma, red cells and liver. There was no effect on the packed cell volume. Guinea pigs weighing 350 g and fed the basal diet for 18 days showed little or no effect on growth rate and food intake, but tissue zinc levels were decreased. Plasma zinc dropped significantly within 24 hours. Platelet aggregation in response to minimal levels of ADP and a prostaglandin endoperoxide analog (U-44069) was severely impaired. Aggregation in response to bovine thrombin (1 unit/ml) was significantly delayed, but the partial response in the presence of indomethacin was not affected by zinc deficiency. The results suggest that impaired platelet aggregation is a general sign of zinc deficiency in mammals and that the function of the physiological eicosanoids is impaired.     

Induction of platelet aggregation in vitro by microbubbles of nitrogen

Microbubbles of nitrogen gas act as a platelet agonist, but the biochemical mechanisms involved in bubble-induced platelet activation are not well known. One characteristic property of a platelet agonist is to potentiate the response by another agonist in a synergistic manner at low concentrations. Possible synergism between N2 gas bubbles and the physiologic agonists ADP, epinephrine, and 5-hydroxytryptamine (5-HT) was tested. The interaction with ADP was additive; N2 microbubbles and ADP had different aggregation profiles, and the bubbles made the reversible ADP aggregation irreversible. Epinephrine caused a strong, synergistic stimulation of bubble-induced platelet aggregation. This synergism was only partially inhibited by indomethacin and acetylsalicylic acid, but abolished by yohimbine. 5-HT had an inhibitory effect on N2 microbubble-induced platelet aggregation. This effect was neutralized by the S2-serotonergic receptor blocker ketanserin. Microbubble stimulation of the platelets before stimulation with ADP, epinephrine, and 5-HT seemed to make them more sensitive to epinephrine only. The strong synergism between microbubbles and epinephrine in vitro should be evaluated for possible future use in predive selection of divers.