Effect of phospholipase A on erythrocyte and thrombocyte aggregation]

A study was made of the effect of plasmin and trypsin on the phospholipase activation, and also of the action of phospholipase A (cobra venom) on the release reaction and the erythrocyte and thrombocyte aggregation. Trypsin and fibrinolysin proved to activate phospholipase, this being accompanied by the accumulation of nonesterified fatty acids in the blood serum. Phospholipase A caused a release of the thromboplastic factor from erythrocytes and thrombocytes and their aggregation. The later is inhibited by albumin and EDTA. It is suggested that the action of the proteolytic enzymes on the blood formed elements was realized through the phospholipase activation.     

Influence of vitamin E on platelet aggregation and thrombocythemia in the rat.

Collagen-induced platelet aggregation was increased in 9-10 wk old vitamin E deficient rats although there was no difference in platelet count between deficient and control animals. With a more prolonged deficiency (at 15 wk) both platelet aggregation and platelet counts were elevated in the vitamin E deficient animals.     

Differential inhibitory effects of vitamin E and other antioxidants on prostaglandin synthetase,platelet aggregation and lipoxidase

Prostaglandin biosynthesis from eicosa-8,11,14-trienoic acid in microsomes from the bovine vesicular gland is inhibited by the antioxidants α-naphthol, guaiacol, NDGA and propyl gallate. Prostaglandin biosynthesis in this system is not inhibited by the antioxidants BHT, DL-α-tocopherol and Trolox C. Arachidonic acid induced platelet aggregation is inhibited specifically by α-naphthol, guaiacol, NDGA and propyl gallate. Both arachidonic acid induced platelet aggregation and ADP induced platelet aggregation are inhibited non-specifically by the antioxidants BHT, DL-α-tocopherol and Trolox C. All antioxidants tested in this study inhibit soybean lipoxidase. Thus α-naphthol, NDGA and propyl gallate are non-specific inhibitors of both prostaglandin synthetase and soybean lipoxidase while BHT, DL-α-tocopherol and Trolox C are specific inhibitors of soybean lipoxidase alone.     

Differential inhibitory effects of vitamin E and other antioxidants on prostaglandin synthetase, platelet aggregation and lipoxidase.

Prostaglandin biosynthesis from eicosa-8,11,14-trienoic acid in microsomes from the bovine vesicular gland is inhibited by the antioxidants alpha-naphthol. guaiacol, NDGA and propyl gallate. Prostaglandin biosynthesis in this system is not inhibited by the antioxidants BHT, DL-alpha-tocopherol and Trolox C. Arachidonic acid induced platelet aggregation is inhibited by specifically by alpha-naphthol. guaiacol, NDGA and propyl gallate. Both arachidonic acid induced platelet aggregation and ADP induced platelet aggregation are inhibited non-specifically by the antioxidants BHT, DL-alpha-tocopherol and Trolox C. All antioxidants tested in this study inhibit soybean lipoxidase. Thus alpha-naphthol, NDGA and propyl gallate are non-specific inhibitors of both prostaglandin synthetase and soybean lipoxidase while BHT, DL-alpha-tocopherol and Trolox C are specific inhibitors of soybean lipoxidase alone.     

Effect of simultaneous administration of vitamin C, L-cysteine and vitamin E on the melanogenesis

The effect of simultaneous administration of vitamin C (ascorbic acid), L-cystein (Cys) and vitamin E (tocopherol) on the melanogenesis in vivo and in vitro was studied. Forty-eight brownish guinea pigs were divided into 4 groups as follows: VC group, VC+Cys group, VC+Cys+VE group and control group. They were given these vitamins by oral administration every day. UV-B exposure (0.384 J/cm2) on their depleted back skin was done at the day 8, 10, 12, 15 17 and 19. After UV-B irradiation, vitamins were administrated further 3 weeks. The luminosity score was measured using a Color Reader CR-11 (Minolta, Co) and the numbers of DOPA-positive melanocytes of their back skin were counted. B16 melanoma cells were incubated with VC, N-acetyl cystein (NAC) and VE. After 4 days of incubation, cells were harvested. The melanin contents and the tyrosinase activities in cells were measured. The luminosity score in the VC+VE+Cys group was higher than those in the other groups. The numbers of DOPA-positive melanocytes of guinea pigs treated with VC, VE and Cys were significantly decreased compared with those in VC group. In B16 melanoma cells, simultaneous treatment of VC, VE and NAC was the most effective to decrease the melanin contents and to inhibit tyrosinase activity.     

Effect of porcine calcitonin on human blood platelet aggregation in vitro]

Porcine calcitonin used in vitro increases ADP and collagene induced aggregation in human platelets.     

A change in erythrocyte membrane permeability in rodents under the influence of fish oil, vitamin E and fatty acids]

In experiments on 370 gerbils (Meriones tamariscinus) and 56 albino rats, studies have been made on the effects of vitamin E, rancid cod-liver oil and unsaturated fatty acids (oleic, oxidated oleic and linoleic) upon the permeability of erythrocyte membrane. Osmotic fragility of erythrocytes to hypotonic NaCl solutions was measured. Seasonal changes in the permeability and sexual differences in these changes were observed. In M. tamariscinus the addition of vitamin E, cod-liver oil and unsaturated fatty acids to the food results in changes of erythrocyte permeability. The pattern of these changes depends on the season of year, differences in nutrition, as well as on fat and tocophenol stores in the organism, which are different in males and females. In albino rats, changes of erythrocyte permeability induced by vitamin E and cod-liver oil are rather insignificant.     

Effects of vitamins A, E, C and P on intensity of blood coagulation in experimental animals]

In experiment on white rats it was shown that preventive 12-day administration of vitamins A, E, C, P decreases the death rate of animals with exogenous thromboplastinemia and reduces hemocoagulative changes, microcirculation disorders, destructive changes of functionally active elements of inner organs. The protective effect of the above vitamins combination in thromboplastinemia is promoted by hypoactivity of platelet aggregation, by low thromboplastic activity of erythrocytes, by limited destruction of vascular endothelium.     

Effect of dietary vitamin E on platelet tocopherol values and 12-lipoxygenase activity

This study was designed to evaluate the effects of different amounts of dietary vitamin E on platelet tocopherol levels and 12-lipoxygenase activity when exogenous arachidonic acid was used as substrate. Weanling male Sprague-Dawley rats were fed diets containing 0, 50, and 5000 ppm of D-alpha-tocopherol acetate for 4 months. Platelet tocopherol was increased with increasing concentrations of dietary vitamin E; however, the conversion of exogenously added arachidonate by platelet to 12-HETE (12-hydroxyeicosatetraenoic acid) and thromboxane B2 from these three dietary groups was essentially the same. This study provides direct evidence that platelet 12-lipoxygenase activity is independent of its vitamin E content when exogenously added arachidonate was used as substrate.     

Zinc,iron, vitamin E,and erythrocyte stability in the rat

Previous studies have shown that deficiencies of zinc and vitamin E, as well as iron excess, contribute to peroxidative damage in several tissues in vivo. The present study reports on the sensitivity of red blood cells from young rats exposed to individual or concurrent imbalances of these three nutrients. For 21 d, rats were fed diets that were either deficient or replete in zinc and with or without excess iron or replete or deficient in vitamin E. When red blood cells from these rats were incubated in vitro, erythrocyte hemolysis, lipid peroxidation (assessed by MDA production), and hemoglobin degradation (assessed by alanine release), did not significantly increase unless vitamin E had been omitted from the diet. These results imply that either adequate tightly-bound zinc exists within the zinc-deficient cell to protect it from oxidative damage, or that other antioxidant defense mechanisms (including vitamin E) present within the plasma membrane and cytosol are sufficient to protect the cell from the otherwise damaging effects of zinc deficiency and/or iron excess.     

Effect of verapamil on platelet aggregation

The influence of the calcium channel blocker verapamil on the aggregation of human blood platelets was studied in vitro in comparison with the calcium channel blocker diltiazem and with the 5-HT antagonist cyproheptadine. Verapamil inhibited the 5-HT-potentiated. ADP-induced aggregation more effectively than the aggregation induced by adrenaline, ADP and collagen. Verapamil antagonized the 5-HT effect in a noncompetitive manner. The same was true of cyprohepatadine which was by more than one order of magnitude more potent than verapamil in inhibiting the 5-HT-induced aggregation. Diltiazem was much less effective than verapamil.     

Effect of erythrocyte aggregation on velocity profiles in venules

A recent whole organ study in cat skeletal muscle showed that the increase in venous resistance seen at reduced arterial pressures is nearly abolished when the muscle is perfused with a nonaggregating red blood cell suspension. To explore a possible underlying mechanism, we tested the hypothesis that red blood cell aggregation alters flow patterns in vivo and leads to blunted red blood cell velocity profiles at reduced shear rates. With the use of fluorescently labeled red blood cells in tracer quantities and a video system equipped with a gated image intensifier, we obtained velocity profiles in venous microvessels (45-75 microm) of rat spinotrapezius muscle at centerline velocities between 0.3 and 14 mm/s (pseudoshear rates 3-120 s(-1)) under normal (nonaggregating) conditions and after induction of red blood cell aggregation with Dextran 500. Profiles are nearly parabolic (Poiseuille flow) over this flow rate range in the absence of aggregation. When aggregation is present, profiles are parabolic at high shear rates and become significantly blunted at pseudoshear rates of 40 s(-1) and below. These results indicate a possible mechanism for increased venous resistance at reduced flows.     

Effect of heparin on platelet aggregation in vitro

Heparin added to citrated platelet rich plasma influences shape change and aggregation of platelets in different ways. In the presence of heparin neither ADP nor collagen induces shape change, while shape change after thrombin or arachidonic acid remains unaltered. Heparin potentiates the first aggregation step induced by ADP and epinephrine but inhibits aggregation induced by thrombin and ristocetin. The second phase of aggregation and the release reaction are not directly influenced by heparin no matter which aggregation agent is used.     

Effect of heparin and heparinoids on platelet aggregation

Biological effectiveness of bovine lung heparin and porcine mucosal heparin was tested in vitro and compared with the effectiveness of 12 semisynthetic heparinoids obtained by sulfation of waste heparin mucopolysaccharides and other biomolecules. Equieffective concentrations of these substances were determined in the sense of prolongation of the thrombin time and the APTT, inhibition of the thrombin- and collagen-induced aggregation, and potentiation of the primary ADP-induced aggregation. The influence of sulfation was proved on the biological effectiveness as well as the significance of the proper choice of the parent structure. Some polycondensates of the polysaccharide type were effective altogether with the sulfated waste heparin mucopolysaccharides. On the contrary, protein structures and low molecular weight glycosides exhibited little or no activity. The effective substances were related to heparin not only by the anticoagulant activity but also by the inhibitory action on the thrombin- and collagen-induced platelet aggregation. Contrary to heparin, higher concentrations of the studied heparinoids strongly potentiated the ADP-induced aggregation response. Strong inhibition of the collagen-induced aggregation was proved after administration of heparin to patients with end-stage renal failure on days without haemodialysis. Less significant changes in the secondary aggregation were observed also after administration of S-heparin (one of the studied heparinoids) to volunteers in the form of the rectal suppositories.     

Effect of ultrafiltrates in plasma from patients with chronic uremia on platelet aggregation]

An effect of 20 ultrafiltrates from patients with chronic renal failure on ADP-, epinephrine-, and arachidonic acid-induced platelet aggregation. Ultrafiltrates were collected at the beginning and the end of dialysis. It was found that ultrafiltrates collected at the beginning of dialysis decrease ADP-induced platelet aggregation whereas ultrafiltrates collected at the and of dialysis exert reverse effect. No effect on epinephrine- and arachidonic acid-induced platelet aggregation was seen. Removal of substances inhibiting platelet aggregation produced by ADP hemodialysis may reveal increased platelet aggregation in patients with uremia.