Effect of Factor XIII on Endothelial Barrier Function

The effect of factor XIII on endothelial barrier function was studied in a model of cultured monolayers of porcine aortic endothelial cells and saline-perfused rat hearts. The thrombin-activated plasma factor XIII (1 U/ml) reduced albumin permeability of endothelial monolayers within 20 min by 30 ± 7% (basal value of 5.9 ± 0.4 × 10−6 cm/s), whereas the nonactivated plasma factor XIII had no effect. Reduction of permeability to the same extent, i.e., by 34 ± 9% could be obtained with the thrombin-activated A subunit of factor XIII (1 U/ml), whereas the iodoacetamide-inactivated A subunit as well as the B subunit had no effect on permeability. Endothelial monolayers exposed to the activated factor XIII A exhibited immunoreactive deposition of itself at interfaces of adjacent cells; however, these were not found on exposure to nonactivated factor XIII A or factor XIII B. Hyperpermeability induced by metabolic inhibition (1 mM potassium cyanide plus 1 mM 2-deoxy-d-glucose) was prevented in the presence of the activated factor XIII A. Likewise, the increase in myocardial water content in ischemic-reperfused rat hearts was prevented in its presence. This study shows that activated factor