Some Properties of the Platelet-Connective Tissue Mixed Agglutination Reaction

204

A B S T R A C T Purified acid-soluble and insoluble human collagen accelerated the clotting of plateletpoor plasma in silicone-treated tubes. The clotpromoting effect did not appear to be due to thromboplastic activity since the collagen preparations did not activate factor X in the presence of factor VII and calcium. Instead, collagen appeared to accelerate clotting by activating Hageman factor (factor XII) on the basis of the following findings: collagen increased the clot-promoting activity of partially purified Hageman factor but exerted no further effect in the presence of kaolin, a known activator of Hageman factor; clot-promoting eluates were obtained from collagen exposed to normal, hemophilic, or PTC-deficient plasma but not from collagen exposed to Hageman or PTA-deficient plasma. The collagen molecule itself appeared to be required for the clot-promoting activity since digestion with collagenase or thermal denaturation at pH 2.5 (about 350C) resulted in very marked reduction in clot-promoting activity. Since thermal denaturation is associated with transformation of collagen structure from triple helical to random coil form, it is suggested that the native form of collagen is essential for the ability to activate Hageman factor.Blockage of the free amino groups by treatment with nitrous acid or dinitrofluorobenzene only slightly reduced the clot-promoting activity of collagen. In contrast, since addition of cationic proteins to collagen markedly reduced pro-coagulant activity it is suggested that negatively charged sites on the collagen molecule are critical for Hageman factor activation. This suggestion is supported by

supporting

confidence: 51%

Activation of hageman factor by collagen

Wilner¹,

Nossel²,

Leroy³

1968

204

“…In addition to activating Hageman factor and thereby initiating intrinsic blood coagulation, collagen causes platelet adherence and aggregation (50)(51)(52). Collageninduced activation of both the coagulation and kallikrein systems raises the possibility that the kallikrein-kinin vasoactive system may function in both hemostatic and thrombotic processes.…”

Section: Discussionmentioning

confidence: 99%

Studies on the Interaction between Collagen and a Plasma Kallikrein-Like Activity EVIDENCE FOR A SURFACE-ACTIVE ENZYME SYSTEM

Harpel¹

1972

A B S T R A C T This study has demonstrated that collagen particles, after exposure to platelet-poor human plasma and subsequent washing, generate a kinin-like agent when incubated with prekinin substrate. The binding of kinin-generating activity to collagen in the plasma collagen incubation mixture occurs rapidly, whereas the loss of this activity in the incubation mixture occurs relatively slowly. The Hageman factor appeared to be necessary for the surface-bound kiningenerating activity, as this activity was absent in collagen exposed to Hageman factor-deficient plasma. These studies have partially characterized the plasma-derived enzymatic activity bound to collagen. Incubation of collagen with plasma caused a concentration-dependent reduction in the kinin-producing activity which was generated by the addition of ellagic acid, a known activator of plasma kallikrein. The kinin-inducing activity bound to collagen is inhibited by soybean trypsin inhibitor, Trasylol, serum C1 inactivator and the plasma a2-macroglobulin, but not by lima bean trypsin inhibitor. An eluate prepared from plasma-treated collagen, when compared with purified plasma kallikrein, shared a similar inhibitor profile. Selective chemical blockage of the free carboxyl groups on the collagen molecule, or heat denaturation, inactivated the ability of the collagen to generate kinin-like activity after incubation with plasma. Removal of the collagen telopeptides or blockage of the free amino groups failed to affect the collagen-plasma interaction. The binding of This study was presented in part at the 44th Scientific

“…Subsequent reactions initiated by the adherence of platelets to connective tissue lead to the formation of a definitive hemostatic plug. Initially, Hugues (1) suggested, as has been repeatedly confirmed in other laboratories (2)(3)(4)(5), that collagen was the specific component of connective tissue to which platelets first adhere.…”

Section: Introductionmentioning

confidence: 98%

Evidence for a Structural Requirement for the Aggregation of Platelets by Collagen

Jaffe¹,

Deykin²

1974

140

A B S T R A C T This study investigates whether soluble collagen can initiate platelet aggregation or whether a higher degree of polymerization is required. Purified rat skin collagen was prepared in four states. Soluble monomeric collagen, containing 2 /hM calcium chloride, was maintained at 4°C until use. A previously uncharacterized form of collagen, soluble microfibrillar collagen, was prepared from monomeric collagen containing calcium chloride by allowing it to polymerize at 230 C. Viscometric and electron microscopic characterization of microfibrillar collagen indicated polymerization to ordered native filaments. Particulate native macrofibrillar collagen was prepared from monomeric collagen by allowing it to polymerize at 37°C in the absence of calcium. Particulate collagen, in which the fibers were randomly associated, was prepared by salt precipitation of calcium-free monomeric collagen. Microfibrillar and native macrofibrillar collagen initiated platelet aggregation, with a lag phase of approximately 60 s. Monomeric collagen initiated aggregation with a lag phase of approximately 180 s. The duration of the lag phase for platelet aggregation initiated by monomeric collagen was independent of the dose. Salt-precipitated particulate collagen did not initiate platelet aggregation. Agents which prolong the transition from monomeric collagen to fibrillar collagen (urea, arginine) retarded or prevented the aggregation of platelets by monomeric collagen. Sodium borohydride, which stabilizes the intraand intermolecular cross-links of collagen did not affect platelet aggregation. Penicillamine, which displaces the intermolecular cross-links and binds the intramolecular cross-links of collagen, did not prevent platelet aggregation. The data suggest that an architectural requirement exists for the initiation of self-perpetuating platelet ag-