Mutalysin II (mut-II) is an alpha-fibrinogenase isolated from Lachesis muta muta (bushmaster)
snake venom. The
enzyme lyses
fibrin clots in vitro, and this activity does not depend on
plasminogen activation. The aim of this study was to assess by intravital microscopy the effect of
Mutalysin II on the recanalization of microvessels after
thrombus induction in the ears of hairless mice. Photochemical
thrombus formation was induced after i.v. injection of 5%
fluorescein isothiocyanate labelled
dextran (
FITC-dextran) followed by
mercury light exposure of individual microvessels of the ear of five anesthetized animals. Video playback analysis of intravital microscopy images of the ear microcirculation permitted us to measure blood flow velocity (microm/s) under control conditions (before
thrombus formation) in the ear microvessels. Thirty minutes after
thrombus formation (blood flow velocity stopped completely), each animal (n=5) was infused with
Mutalysin II (2.0 mg/kg, i.v.). All animals treated with
Mutalysin II showed evident thrombolysis after approximately 12 min, followed by recanalization. A separate group of mice (n=5) which received
urokinase type-plasminogen activator (
u-PA, 250 U/mouse, i.v.) showed blood flow restoration within the same interval (12 min). These in vivo data suggest that
Mutalysin II has the potential to be an effective
thrombolytic agent.