OBJECTIVE: During the last decade, experimental and clinical evidence has accumulated that antithrombin (AT) exerts anti-inflammatory effects when given in high doses. Meanwhile, AT substitution has been shown to significantly increase prostacyclin release. However, the link between endothelial AT binding and anti-inflammatory AT effects remains to be established in vivo, although heparin has been shown to counteract anti-inflammatory AT effects. We hypothesized that the administration of heparin in endotoxin-challenged rats would decrease endothelial AT binding and systemic prostacyclin concentrations. DESIGN: Prospective, randomized, controlled experimental in vivo study. SETTING: Research laboratory of a university hospital. ANIMALS: Fifty-six Wistar rats. INTERVENTIONS: Baseline values of coagulation variables were measured in six animals. Forty of 50 Wistar rats in the study groups were given endotoxin (50 mg x kg(-1) iv) and were treated with saline (group LPS), AT (15 units x kg(-1) x hr(-1)) (LPS+AT), AT and heparin (80 IU x kg(-1) x hr(-1)), or AT and hirudin (0.12 mg x kg(-1) x hr(-1)); the other 10 received saline instead of endotoxin and were treated with AT alone. Before endotoxin application, a tracheostomy was performed, and venous and arterial catheters were inserted for blood sampling and infusion. MEASUREMENTS: Intravital endothelial AT binding was studied by using fluorescence isothiocyanate-marked antibodies during intravital microscopy of intestinal submucosal venules. Systemic prostacyclin, thrombin-AT complex, and fibrinogen concentrations were measured after 4 hrs. Intergroup differences were tested by Kruskal-Wallis analysis of variance on ranks. MAIN RESULTS: AT and AT + heparin were equally effective in inhibiting systemic procoagulant turnover as reflected by fibrinogen concentrations. Only the administration of AT + hirudin significantly prevented fibrinogen consumption (p < .05). In contrast with all other treatments, the administration of heparin significantly reduced intravital endothelial AT binding (p < .05). However, prostacyclin concentrations were similarly increased in all endotoxin-challenged study groups irrespective of the anticoagulatory treatment. CONCLUSIONS: There is evidence that heparin in contrast with hirudin prevents AT from being bound to the endothelial cell surface in this experimental model. Under low-dose AT substitution, systemic prostacyclin concentrations do not depend on whether heparin or hirudin is used for thrombin inhibition. These results support the view that heparin may counteract anti-inflammatory AT effects by keeping AT away from its endothelial binding sites; however, the results question the view that decreased endothelial prostacyclin release is solely responsible.
OBJECTIVE: During the last decade, experimental and clinical evidence has accumulated that antithrombin (AT) exerts anti-inflammatory effects when given in high doses. Meanwhile, AT substitution has been shown to significantly increase prostacyclin release. However, the link between endothelial AT binding and anti-inflammatory AT effects remains to be established in vivo, although heparin has been shown to counteract anti-inflammatory AT effects. We hypothesized that the administration of heparin in endotoxin-challenged rats would decrease endothelial AT binding and systemic prostacyclin concentrations. DESIGN: Prospective, randomized, controlled experimental in vivo study. SETTING: Research laboratory of a university hospital. ANIMALS: Fifty-six Wistar rats. INTERVENTIONS: Baseline values of coagulation variables were measured in six animals. Forty of 50 Wistar rats in the study groups were given endotoxin (50 mg x kg(-1) iv) and were treated with saline (group LPS), AT (15 units x kg(-1) x hr(-1)) (LPS+AT), AT and heparin (80 IU x kg(-1) x hr(-1)), or AT and hirudin (0.12 mg x kg(-1) x hr(-1)); the other 10 received saline instead of endotoxin and were treated with AT alone. Before endotoxin application, a tracheostomy was performed, and venous and arterial catheters were inserted for blood sampling and infusion. MEASUREMENTS: Intravital endothelial AT binding was studied by using fluorescence isothiocyanate-marked antibodies during intravital microscopy of intestinal submucosal venules. Systemic prostacyclin, thrombin-AT complex, and fibrinogen concentrations were measured after 4 hrs. Intergroup differences were tested by Kruskal-Wallis analysis of variance on ranks. MAIN RESULTS: AT and AT + heparin were equally effective in inhibiting systemic procoagulant turnover as reflected by fibrinogen concentrations. Only the administration of AT + hirudin significantly prevented fibrinogen consumption (p < .05). In contrast with all other treatments, the administration of heparin significantly reduced intravital endothelial AT binding (p < .05). However, prostacyclin concentrations were similarly increased in all endotoxin-challenged study groups irrespective of the anticoagulatory treatment. CONCLUSIONS: There is evidence that heparin in contrast with hirudin prevents AT from being bound to the endothelial cell surface in this experimental model. Under low-dose AT substitution, systemic prostacyclin concentrations do not depend on whether heparin or hirudin is used for thrombin inhibition. These results support the view that heparin may counteract anti-inflammatory AT effects by keeping AT away from its endothelial binding sites; however, the results question the view that decreased endothelial prostacyclin release is solely responsible.
Authors: Jordan Kountchev; Klaudija Bijuklic; Romuald Bellmann; Christian J Wiedermann; Michael Joannidis Journal: Crit Care Date: 2005-09-19 Impact factor: 9.097