Effects of histones and dextran on some properties of fibrin, particularly on its susceptibility to plasmin

Abstract

F2a + F3 arginine-rich and F1 lysine-rich fractions of calf thymus histones as well as dextran 65 were investigated for their ability to affect the properties of fibrinogen and fibrin. F2a + F3 histone fraction in low concentrations was shown to precipitate soluble fibrin as well as fibrinogen. Dextran was found much less effective and F1 histone fraction completely inactive in this respect. F2a + F3 fraction and dextran induced a dose dependent increase of fibrin opacity and decrease in the rate of 125I-fibrin proteolysis by plasmin. Both histone fractions were demonstrated to neither inhibit the caseinolytic activity of plasmin nor to act as substrates for this enzyme. Therefore increased resistance to lysis of fibrin clot formed in the presence of F2a + F3 fraction or of dextran seemed to result from an altered structure of fibrin but not from the inhibition of plasmin proteolytic activity. We were not able to confirm the recently described increase of the susceptibility of fibrin plates containing dextran to lysis by plasmin.