Fibrinogen and fragment D-induced vascular constriction

Elevated fibrinogen (Fg) concentration in blood is a high risk factor for many cardiovascular diseases. We hypothesize that Fg and its early degradation product, fragment D, may result in arterial constriction by binding endothelial intercellular adhesion molecule-1 (ICAM-1). The vasoconstriction induced by Fg and fragment D was studied in third- and second-order arterioles (3As and 2As, respectively) of Sprague-Dawley rat cremaster muscle in vivo, in aortic and femoral artery rings, and in the segments of first-order arterioles (1As) isolated from rat cremaster muscle. Intravascular infusion of Fg induced significant constriction of 3As and 2As (by 33.4 +/- 3.4 and 23.7 +/- 4.3%, respectively) in vivo and was abolished in the presence of the specific endothelin type A receptor blocker BQ-610. Fg and fragment D produced significant constriction of both aortic and femoral artery rings. Isolated 1As constricted in response to Fg (0.3 microM) and fragment D (3 microM) by 31 +/- 1.4 and 12 +/- 1.5%, respectively. Fluorescently labeled Fg and fragment D bound to the vascular wall, whereas albumin bound to a significantly lesser degree. The binding of Fg and fragment D to the arteriolar wall and constriction of aortic and femoral artery rings as well as isolated 1As were abolished in the presence of anti-Fg and anti-ICAM-1 antibodies. These results indicate that binding of Fg and fragment D to the vascular wall through ICAM-1 may contribute to the increased vascular tone and resistance that compromise circulation.