[The vasomotor effects of the enzymes of the fibrinolytic system in rats].

Human plasmin (Pm) caused a rapid dose-dependent relaxation of norepinephrine-preconstricted isolated aortic ring and vascular net in the Wistar rat hindlimbs. Neither atropine, nor obsidan or indomethacin suppressed the Pm-induced vasodilatation of the aortic ring. Mechanical removal of endothelium and NO-blocker N-Nitro-L-Arg almost completely abolished the Pm-induced relaxation. DIP-Pm, AN-Pm and Glu-plasminogen did not change the vascular tone of the preconstricted rings. Both aprotinin and E-aminocapronic acid inhibited the relaxing effect of the Pm. Besides the circulating Pm, the enzyme forming on the endothelial surface from plasminogen under the action of urokinase, produced the vascular dilatation as well.