Enhancement of the permeability-increasing effect of bradykinin and substance P by a peptide derived from fibrinogen.

Two low molecular weight fibrin(ogen) degradation products, 6A (Ala-Arg-Pro-Ala-Lys) and 6D (Ser-Gln-Leu-Gln-Lys-Val-Pro-Pro-Glu-Trp-Lys) that are known to increase vascular permeability were injected together with bradykinin, substance P, neurotensin, histamine or tuftsin into the dorsal skin of rats. Effects on microvascular permeability were evaluated as leakage of intravenously injected 125I-labelled human serum albumin to tissues. It was found that peptide 6A potentiated the leakage caused by bradykinin and also, to a minor extent, that caused by substance P over a 30 min period, but not of any other substance. Peptide 6D increased bradykinin-induced leakage to a lower degree than did peptide 6A. Thus, it is shown that products resulting from fibrinolysis exert a selective effect upon the action of bradykinin and of substance P.