THE PERMEABILITY OF FIBRIN NETWORK DEVELOPED IN HUMAN PLASMA

Fibrin network permeability has an important role in thrombosis and in flammation since it influences the rate of transport of macromolecules through the network by convection. The conditions of polymerization o f fibrin determine the network permeability and this has been attribut ed to variability in fibrin fibre thickness. Inconsistencies between v alues for fibrin fibre thickness derived from turbidity and permeabili ty were examined. Networks were developed from human plasma by the add ition of thrombin and network polymerization was modified pharmacologi cally. Dextran (MW 70 000) and poloxamer 188 both increased, and laury l sulphate decreased, network permeability and network turbidity. Netw ork fibre thickness was consistently higher when derived from permeabi lity than from turbidity. Network permeability was significantly more susceptible to pharmacological manipulation by these agents than netwo rk turbidity. These inconsistencies were attributed to variation in th e arrangement of the network fibres such as inhomogeneity of network f ibre distribution and to fibre aggregation or alignment. Collectively these factors prohibit the derivation of fibrin fibre thickness from p ermeability. The dimensionless permeability (network permeability/(fib re radius)(2)) was used as an index of network fibre arrangement and f ound to be readily modified pharmacologically. Physiological and pharm acological regulation of fibrin network permeability may be predominan tly mediated through modification of fibre arrangement and not through fibre thickness.