Some Inhibitors of the Fibrinogen-Fibrin Conversion

Summary

1. The inhibitory effect of a number of substances on the fibrinogen-thrombin reaction has been studied. The effect is best observed at pH 7.4 using calcium free dilute thrombin. Ca⁺⁺ reduces the effect; Mg⁺⁺ is less effective than Ca⁺⁺. The optimum concentration of Ca⁺⁺ is 0.5 to 1 mM.

2. Preincubation with fibrinogen increases the effect of EDTA, sulphite and thioglycollate on the thrombin time. These compounds also appear to alter fibrinogen and thereby retard the conversion of fibrinogen to fibrin monomer.

3. Preincubation of thrombin with these substances does not result in loss of TAME esterolytic activity or in prolongation of thrombin time of fibrinogen.

4. Inhibitors of the fibrinogen-thrombin reaction retard the polymerisation of fibrin monomer to fibrin and also the attendant increase in opacity.

5. The inhibitors of the fibrinogen-thrombin reaction studied appear to exert their effect mostly at the stage of polymerisation of the fibrin monomer. Calcium ions largely reverse the inhibition of this step.

^* Present address : Medizinische Klinik, University of Münster (Westf.), W. Germany.

• References

• Biggs R, Macfarlane R. G. Human Blood Coagulation and its Disorders. 3rd. edn. 36 Blackwell Scientific Publications; Oxford: 1962
• Bithel T. C. A study of the inhibitory effect of Ethylene diamine tetraacetic acid on the ThrombinFibrinogen reaction. Biochem. J. 93: 431 1964;
• Daughaday W. H, Lowry O. H, Rosebrough N. J, Fields W. S. Determination of cerebro spinal fluid protein with the Folin phenol reagent. J. Lab. clin. Med. 39: 663 1952;
• Donnelly T. M, Laskowski Jr. M, Notley N, Scheraga H. A. Fibrinogen-Fibrin Conversion II. Arch. Biochem. 56: 369 1955;
• Edsall J. T, Lever W. Effect of ions and neutral molecules on fibrin clotting. J. biol. Chem. 191: 735 1951;
• Fantl P, Nance M. H. Influence of 2.3 Dimercaptopropanol (BAL) on Blood Coagulation. Nature (Lond) 159: 777 1947;
• Ferry J. D. Polymerisation of Fibrinogen. Physiol. Rev. 34: 753 1954;
• Ferry J. D, Morrison P. R. Preparation and properties of serum and plasma proteins. VIII. The conversion of fibrinogen to fibrin under various conditions. J. Amer. chem. Soc. 69: 388 1947;
• Ferry J. D, Shulman S. The conversion of fibrinogen to fibrin-I. Influence of hydroxyl compounds on clotting time and clot opacity. J. Amer. chem. Soc. 71: 3198 1949;
• Hawk P. B, Oser B. L, Summerson W. H. Practical Physiological Chemistry. 13th. edn. 491 Mc Graw Hill Book Company; New York: 1954
• Katz S, Shulman S, Tinoco Jr. I, Billick I. J, Gutfreund K, Ferry J. D. The conversion of fibrinogen to fibrin. XIV. The effect of calcium on the formation and dissociation of intermediate polymers. Arch. Biochem. 47: 165 1953;
• Loewy A. G, Gallant J. A, Dunathan K. Fibrinase IV. Effect on fibrin solubility. J. biol. Chem. 236: 2648 1961;
• Seegers W. H. Prothrombin. 414 Harvard University Press; Cambridge, Mass: 1962
• Shulman S. The conversion of fibrinogen to fibrin. IV. Reversible inhibition of the reaction. Arch. Biochem. 30: 353 1951;
• Shulman S, Katz S, Ferry J. D. The conversion of fibrinogen to fibrin. XIII. Dissolution of fibrin and inhibition of clotting by various neutral salts. J. gen. Physiol. 36: 759 1953;