Species specificity in the acceleration of tissue-type plasminogen activator-mediated activation of plasminogens, by fibrinogen cyanogen bromide fragments

Activation of human plasminogen by human tissue-type plasminogen activator (t-PA) is accelerated in the presence of cyanogen bromide digests of human fibrin(ogen).

In the present study a possible species specificity of this phenomenon was investigated. All combinations of the plasminogens, fibrin monomers and cyanogen bromide digests of the fibrinogens of man, pig, rat, cat and monkey (Macaca mulatta), and three t-PA species (man, rat and pig) were studied.

No species differences were noted with the fibrin monomers i.e. the activation rate of all five plasminogens increased more than 20-fold in the presence of all five fibrin monomer species, irrespective if man, rat or pig t-PA was used.

However, we found that species specificities come to expression when cyanogen bromide digests of the corresponding fibrinogens were used as accelerators.

Our results indicate that the plasminogen species and not the source of t-PA or fibrinogen dictates if accelerated activation occurs in the presence of a fibrinogen CNBr digest. The plasminogens can be roughly divided in two groups:

- One group, comprising human, monkey and cat plasminogen, which are activated at a higher rate by all three t-PA species in the presence of fibrinogen digest independent on the fibrinogen species from which the digest was prepared.

- An other group, comprising pig and rat plasminogen, which is not or only marginally faster activated by the three t-PA species, irrespective of the fibrinogen species from which the CNBr digest was prepared.