Fluid Phase Coagulation Events Have Minimal Impact on Plasma Fibrin Structure

Greilich

1996

SummaryAlthough snake venom enzymes such as reptilase do not cause viscous metamorphosis, platelet secretion or clot retraction; when batroxobin and calcium are added to citrated blood significant platelet force development occurs. When this batroxobin-calcium system was applied to the study of platelet function during cardiopulmonary bypass (CPB), force development was found to be completely inhibited. After heparin reversal by protamine sulfate, significant recovery of force occurred. The present investigation was performed to evaluate the role of heparin in reducing force development during CPB. At concentrations above 0.10 U/ml, heparin totally suppressed force development in normal plasma. Addition of protamine sulfate to heparinized plasma caused complete recovery of force development. These concentrations of heparin had little effect on platelet aggregation by ADP or collagen. Possible direct effects of heparin on fibrin assembly and structure were studied by adding varying amounts of heparin to plasma and then inducing clot formation with batroxobin. At 1 U/ml, heparin reduced the size of fibrin fibers by 33%. Higher heparin concentrations had no additional effect. These results indicate that heparin may be responsible for a significant component of the decreased platelet force noted during cardiopulmonary bypass. To test whether heparin’s effect could be due to suppression of thrombin activity, the effects of the antithrombin hirudin on force development were measured. Hirudin also inhibited force development in a concentration dependent manner. Thus, heparin’s reduction of platelet force development may be due, at least in part, to suppression of thrombin activity.

Section: Discussionmentioning

confidence: 99%

Heparin Ablates Force Development during Platelet Mediated Clot Retraction

Greilich

1996

“…Finally, it is possible that fibrin formed in plasma might be influenced by the presence of other clotting factors. We recently investigated this possibility, and found that plasma fibrin formed by activation of the iutrinsic clotting system is identical to fibrin formed by the direct addition of thrombin (33). In both situations, plasma fibrin is composed of fibers larger than those formed from purified fibrinogen.…”

Section: Discussionmentioning

confidence: 99%

Fibrin Formed in Plasma is Composed of Fibers More Massive than those Formed from Purified Fibrinogen

1988

SummaryReports of altered fibrin resulting from interactions with plasma proteins and cellular release products have raised the possibility that plasma fibrin may differ from purified fibrin. To investigate this possibility, the structures of thrombin-induced gels formed from platelet poor plasma and from purified fibrinogen were compared using turbidity and gel perfusion techniques. Plasma gels formed more slowly and were composed of fibers two to four times more massive than gels formed from purified fibrinogen. Increasing calcium concentration, decreasing ionic strength, decreasing thrombin concentration, or increasing fibrinogen concentration resulted in increasing fiber size. Addition of excess thrombin accelerated plasma gel formation and decreased gel fiber size, but did not totally eliminate the structural differences between the two systems. Thus, antithrombin activity, while possibly contributory, is not solely responsible for the altered gel structure. Penetration of plasma gels by fibrinolytic agents, egress to areas of injury by inflammatory cells, and gel removal by plasmin are processes at least partially dependent on gel fiber and pore size.

“…Fibrin gels formed from plasma are composed of thicker fibers than purified fibrin clots formed under identical conditions of calcium concentration, ionic strength, and pH (20). This is true whether plasma clotting is initiated by the addition of exogenous thrombin or by activation of the intrinsic cascade (20,29). Fibrin formed in the presence of erythrocytes is virtually identical to plasma fibrin in terms of fiber size (30).…”

Section: Discussionmentioning

confidence: 99%

Effect of Glycosaminoglycans on Thrombin- and Atroxin-Induced Fibrin Assembly and Structure

Powers

1989

SummaryThis study was performed to quantitate the impact of several glycosaminoglycans (GAG) on fibrin assembly and structure. Gel formation was monitored as the increase in optical density at 633 nm subsequent to thrombin (2 NIH u/ml) or atroxin (0.10 mg/ml) addition to solutions of buffered fibrinogen (1 mg/ml) or plasma. Gel absorbance was measured as a function of wavelength (400 to 800 nm) and gel fiber diameter and mass/length ratio (μ) were calculated. Chondroitin sulfate A (CSA)shortened the lag phase, enhanced the maximal rate of turbidity increase, and increased the final gel turbidity of fibrin gels formed by thrombin or atroxin. CSA (16 mg/ml) increased fiber μ from 1.3 to 3.1 × 1013 dalton/cm and fiber radius from 6.0 to 8.6 × 10-6 cm in thrombin-induced gels. μ increased from 0.7 to 2.7 × 1013 dalton/cm and fiber radius from 4 to 7.8 × 10-6 cm for atroxin-induced gels. Above 16 mg/ml, CSA caused fibrinogen precipitation in purified solutions but not in plasma. CSA inhibited thrombin-induced plasma clotting of plasma but effects in atroxin-mediated plasma gels paralleled those seen in purified solutions. Chondroitin sulfate B (CSB)-induced changes in fibrin were similar but slightly less dramatic than those seen with CSA. μ increased from 0.9 to 2.0 × 1013 dalton/cm for thrombin-induced fibrin gels and from 0.8 to 2.3 × 1013 dalton/cm for atroxininduced gels. Low molecular weight heparin (Mr = 5100) slowed fibrin assembly and reduced fiber size by 50% in thrombininduced gels. Changes in μ of atroxin-induced gels were much less pronounced (<20%). This study documents pronounced GAGinduced changes in fibrin structure which vary with GAG species and may mediate significant physiologic functions.