TISSUE PLASMINOGEN-ACTIVATOR RELEASE INVIVO IN RESPONSE TO VASOACTIVE AGENTS

  • 1 January 1985
    • journal article
    • research article
    • Vol. 66  (4) , 835-839
Abstract
Release of tissue plasminogen activator into the circulation of rats in response to intravascular injections of vasoactive agents is studied by using a sensitive and specific clot lysis assay. Intra-arterial bradykinin elicits a rapid and transient rise in circulating plasminogen activator, which is maximum within 1 minute and is cleared within 4 to 8 minutes. The plasminogen activator is fibrin dependent and is cleared 4 to 8 minutes. The plasminogen activator is fibrin dependent and is neutralized by an antiserum to human tissue-type plasminogen activator. Bradykinin is 1,000-fold more potent than the other agonists tested, which include histamine, norepinephrine, epinephrine, eledoisin-related peptide, arginine-vasopressin, lysine-vasopressin, desmopressin acetate, carbacol, and acetylcholine. Potency of bradykinin is related to its amino acid sequence. Sequential infusions of bradykinin produce a tachyphylactoid response that could be overcome by increasing the dose of the sequential bradykinin challenge. It is concluded that the characteristics of the responses to bradykinin and other agents in vivo differ significantly from those observed in isolated tissue preparations.