Coronary thrombolysis with Desmodus salivary plasminogen activator in dogs. Fast and persistent recanalization by intravenous bolus administration.

BACKGROUND: DSPA (Desmodus salivary plasminogen activator) is a new thrombolytic agent corresponding to a natural plasminogen activator discovered in the saliva of the vampire bat Desmodus rotundus. Compared with tissue plasminogen activator (TPA), DSPA, produced in a recombinant cell line, is more fibrin cofactor dependent than TPA. METHODS AND RESULTS: The thrombolytic properties of DSPA and TPA were compared in a canine model of copper coil-induced coronary thrombosis. All dogs received heparin 200 IU/kg IV and SC. Whereas controls did not reperfuse within 180 minutes (none of six), intravenous bolus administration of DSPA at 25, 50, and 100 micrograms/kg resulted in a 100% incidence (6 of 6) of recanalization within 37, 23, and 18 minutes, respectively. TPA at 63 and 125 micrograms/kg reopened the coronaries in 33% (two of six) and 50% (three of six) of cases within 40 minutes. Eighty-three percent (5 of 6) of the arteries were still patent 3 hours after 50 and 100 micrograms/kg DSPA, whereas only 20% (one of five) of all coronaries originally recanalized with both doses of TPA were still open at 3 hours. Plasma levels of alpha 2-antiplasmin decreased significantly only with 125 micrograms/kg TPA. The clearance of DSPA (2.3 to 3.5 mL.min-1.kg-1) was lower compared with TPA (11.4 to 20 mL.min-1.kg-1) due to a prolonged terminal half-life. CONCLUSIONS: In a canine coronary thrombosis model, DSPA exhibited higher potency and recanalized coronary arteries faster and with a lower incidence of reocclusion than TPA. Its properties may translate into a higher efficacy in patients compared with available thrombolytic agents. The long half-life of DSPA may allow for single bolus administration in the treatment of acute myocardial infarction.

Plasminogen activators from the saliva of Desmodus rotundus (common vampire bat): unique fibrin specificity.

The saliva of D. rotundus contains at least four plasminogen activators (PAs) which all require fibrin as a cofactor. D. rotundus salivary PAs (DSPAs) exhibit a sequential array of structural motifs such as "Finger" (F), "EGF" (E), "Kringle" (K) and "Protease" (P) which was elucidated by cDNA cloning and sequencing. The respective domain organizations are: FEKP (DSPA alpha 1 and DSPA alpha 2), EKP (DSPA beta) and KP (DSPA gamma). In all four forms the plasmin-sensitive site of tPA is obliterated, indicating that they function as single-chain enzymes. DSPA alpha 1 differs from alpha 2 by amino acid substitutions found mainly in the F, E and K domain, 11% of the total sequence. DSPA beta and gamma, while being closely related to alpha 2, still exhibit 2 and 13 amino acid exchanges, respectively. These sequence heterogeneities, together with results of Southern blot hybridization experiments, strongly suggest that the four DSPA mRNA species originate from different genes. All four forms of DSPA have been expressed in animal cell culture and DSPA alpha 1 was chosen for a detailed pharmacological characterization. In vitro DSPA alpha 1 activity is enhanced 50,000-fold in the presence of fibrin, whereas the activity of single chain tPA is only enhanced 100-fold. At equally effective thrombolytic doses DSPA causes lower bleeding incidence in a rat mesenteric vein model and exhibits high potency, clot selectivity, and speed in the dissolution of fibrin embolized into the lung of anesthetized rats. In the copper coil-induced dog coronary heart infarction model, at doses that achieve patency at equal rates, reocclusion is significantly less frequent than with tPA. These results indicate that DSPA alpha 1 may be a safer and more efficacious thrombolytic agent than the PAs currently in clinical use.

Thrombolytic properties of Desmodus rotundus (vampire bat) salivary plasminogen activator in experimental pulmonary embolism in rats.

rDSPA alpha 1 (recombinant Desmodus salivary plasminogen activator alpha 1) is a recombinant protein corresponding to a natural plasminogen activator from the vampire bat Desmodus rotundus. The thrombolytic properties of rDSPA alpha 1 and tissue-type plasminogen activator (t-PA) were compared in a rat model of pulmonary embolism. Whole blood clots, produced in vitro and labeled with 125I-fibrinogen, were embolized into the lungs of anesthetized rats. Thrombolysis was calculated from the difference between initial clot radioactivity and that remaining in the lungs at 60 minutes. Blood was sampled for gamma counting, measurement of hemostatic factors, and plasminogen activator antigen levels. Thrombolysis at 3, 10, 30, and 100 nmol/kg intravenously (10% bolus, 90% over 60 minutes) amounted to 30% +/- 2%, 51% +/- 4%, 85% +/- 4%, 98% +/- 0% for rDSPA alpha 1 and 30% +/- 3%, 41% +/- 3%, 57% +/- 6%, 93% +/- 2% for t-PA (controls: 29% +/- 2%; mean +/- SEM, n greater than or equal to 6). t-PA at 100 nmol/kg significantly decreased fibrinogen, plasminogen, and alpha 2-antiplasmin levels by 33% +/- 7%, 38% +/- 8%, and 61% +/- 9%, whereas rDSPA alpha 1 at 100 nmol/kg only lowered alpha 2-antiplasmin significantly (by 29% +/- 6%). Compared with t-PA, rDSPA alpha 1 is the more potent and more clot selective (fibrin specific) thrombolytic agent. These results suggest that rDSPA alpha 1 may be safer and more efficacious than currently used thrombolytics.

Potential therapeutic mechanisms of stable prostacyclin (PGI2)-mimetics in severe peripheral vascular disease.

In 2 randomized, double-blind studies, 109 diabetic patients with trophic lesions and 101 non-diabetics suffering from peripheral vascular disease (PVD) stage IV (Fontaine) received daily 6-hour i.v. infusions of iloprost (less than or equal to 2ng/kg/min) or of placebo over 28 days. Iloprost treatment was superior to placebo, showing ulcer healing in more than 60% of patients compared to less than 25% in the control group. The beneficial effects were sustained during a 1 year follow-up period. Platelet activation, adhesion, aggregation and release reaction on atherosclerotic lesions, impaired microvascular perfusion, loss of microvascular barrier function, increased white blood cell - vessel wall interaction and hemorheological disturbances are all believed to play a role in PVD. Stable PGI2-mimetics inhibit platelet activation by all endogenous mediators as well as platelet release of mitogenic factors (PDGF).

The distribution of monosaccharides and hexosamines in the oviduct of Salamandra salamandra (L.) (Amphibia, Urodela).

Biochemical analysis of the different segments of the oviduct in the ovoviviparous salamander, Salamandra salamandra, reveals the monosaccharides glucose, galactose, fucose, mannose, ribose and the hexosamines glucosamine and mannosamine. In segment 1 (pars recta) ribose and mannose are absent, and in segments 2 (p. convoluta I) and 5 (p. convoluta IV, uterus) mannose is not detectable; fucose is absent in the uterus. Segments 3 (p. convoluta II) and 4 (p. convoluta II) contain all sugars identified. The main hexoses present in the glandular segments are galactose, fucose and glucose.